Integrate linkedin API part 2

linkedin-logoSomeday ago I was working in a site, where I’ve  implemented many features of linkedin via their API using PHP language. Linkedin has updated their API, they also introduced new Javascript based API and widgets . Javascript based api is very easy to integrate and widget is far easier than others.

Whatever, in this article I’ll update and inform you about some new functions I added in the old php library. First of all, if you want to read this article first read the old one where you’ll be informed about how to integrate linkedin, get token to use api  call and then come back here.

In that article I borrowed 2 files from other developers that I used my first tutorial also:

  1. oAuth.php from Abraham
  2. linkedin.php from Andy Smith

Here are those files:

<?php
// vim: foldmethod=marker

/* Generic exception class
 */
class OAuthException extends Exception {
  // pass
}

class OAuthConsumer {
  public $key;
  public $secret;

  function __construct($key, $secret, $callback_url=NULL) {
    $this->key = $key;
    $this->secret = $secret;
    $this->callback_url = $callback_url;
  }

  function __toString() {
    return "OAuthConsumer[key=$this->key,secret=$this->secret]";
  }
}

class OAuthToken {
  // access tokens and request tokens
  public $key;
  public $secret;

  /**
   * key = the token
   * secret = the token secret
   */
  function __construct($key, $secret) {
    $this->key = $key;
    $this->secret = $secret;
  }

  /**
   * generates the basic string serialization of a token that a server
   * would respond to request_token and access_token calls with
   */
  function to_string() {
    return "oauth_token=" .
           OAuthUtil::urlencode_rfc3986($this->key) .
           "&oauth_token_secret=" .
           OAuthUtil::urlencode_rfc3986($this->secret);
  }

  function __toString() {
    return $this->to_string();
  }
}

/**
 * A class for implementing a Signature Method
 * See section 9 ("Signing Requests") in the spec
 */
abstract class OAuthSignatureMethod {
  /**
   * Needs to return the name of the Signature Method (ie HMAC-SHA1)
   * @return string
   */
  abstract public function get_name();

  /**
   * Build up the signature
   * NOTE: The output of this function MUST NOT be urlencoded.
   * the encoding is handled in OAuthRequest when the final
   * request is serialized
   * @param OAuthRequest $request
   * @param OAuthConsumer $consumer
   * @param OAuthToken $token
   * @return string
   */
  abstract public function build_signature($request, $consumer, $token);

  /**
   * Verifies that a given signature is correct
   * @param OAuthRequest $request
   * @param OAuthConsumer $consumer
   * @param OAuthToken $token
   * @param string $signature
   * @return bool
   */
  public function check_signature($request, $consumer, $token, $signature) {
    $built = $this->build_signature($request, $consumer, $token);
    return $built == $signature;
  }
}

/**
 * The HMAC-SHA1 signature method uses the HMAC-SHA1 signature algorithm as defined in [RFC2104]
 * where the Signature Base String is the text and the key is the concatenated values (each first
 * encoded per Parameter Encoding) of the Consumer Secret and Token Secret, separated by an '&'
 * character (ASCII code 38) even if empty.
 *   - Chapter 9.2 ("HMAC-SHA1")
 */
class OAuthSignatureMethod_HMAC_SHA1 extends OAuthSignatureMethod {
  function get_name() {
    return "HMAC-SHA1";
  }

  public function build_signature($request, $consumer, $token) {
    $base_string = $request->get_signature_base_string();
    $request->base_string = $base_string;

    $key_parts = array(
      $consumer->secret,
      ($token) ? $token->secret : ""
    );

    $key_parts = OAuthUtil::urlencode_rfc3986($key_parts);
    $key = implode('&', $key_parts);

    return base64_encode(hash_hmac('sha1', $base_string, $key, true));
  }
}

/**
 * The PLAINTEXT method does not provide any security protection and SHOULD only be used
 * over a secure channel such as HTTPS. It does not use the Signature Base String.
 *   - Chapter 9.4 ("PLAINTEXT")
 */
class OAuthSignatureMethod_PLAINTEXT extends OAuthSignatureMethod {
  public function get_name() {
    return "PLAINTEXT";
  }

  /**
   * oauth_signature is set to the concatenated encoded values of the Consumer Secret and
   * Token Secret, separated by a '&' character (ASCII code 38), even if either secret is
   * empty. The result MUST be encoded again.
   *   - Chapter 9.4.1 ("Generating Signatures")
   *
   * Please note that the second encoding MUST NOT happen in the SignatureMethod, as
   * OAuthRequest handles this!
   */
  public function build_signature($request, $consumer, $token) {
    $key_parts = array(
      $consumer->secret,
      ($token) ? $token->secret : ""
    );

    $key_parts = OAuthUtil::urlencode_rfc3986($key_parts);
    $key = implode('&', $key_parts);
    $request->base_string = $key;

    return $key;
  }
}

/**
 * The RSA-SHA1 signature method uses the RSASSA-PKCS1-v1_5 signature algorithm as defined in
 * [RFC3447] section 8.2 (more simply known as PKCS#1), using SHA-1 as the hash function for
 * EMSA-PKCS1-v1_5. It is assumed that the Consumer has provided its RSA public key in a
 * verified way to the Service Provider, in a manner which is beyond the scope of this
 * specification.
 *   - Chapter 9.3 ("RSA-SHA1")
 */
abstract class OAuthSignatureMethod_RSA_SHA1 extends OAuthSignatureMethod {
  public function get_name() {
    return "RSA-SHA1";
  }

  // Up to the SP to implement this lookup of keys. Possible ideas are:
  // (1) do a lookup in a table of trusted certs keyed off of consumer
  // (2) fetch via http using a url provided by the requester
  // (3) some sort of specific discovery code based on request
  //
  // Either way should return a string representation of the certificate
  protected abstract function fetch_public_cert(&$request);

  // Up to the SP to implement this lookup of keys. Possible ideas are:
  // (1) do a lookup in a table of trusted certs keyed off of consumer
  //
  // Either way should return a string representation of the certificate
  protected abstract function fetch_private_cert(&$request);

  public function build_signature($request, $consumer, $token) {
    $base_string = $request->get_signature_base_string();
    $request->base_string = $base_string;

    // Fetch the private key cert based on the request
    $cert = $this->fetch_private_cert($request);

    // Pull the private key ID from the certificate
    $privatekeyid = openssl_get_privatekey($cert);

    // Sign using the key
    $ok = openssl_sign($base_string, $signature, $privatekeyid);

    // Release the key resource
    openssl_free_key($privatekeyid);

    return base64_encode($signature);
  }

  public function check_signature($request, $consumer, $token, $signature) {
    $decoded_sig = base64_decode($signature);

    $base_string = $request->get_signature_base_string();

    // Fetch the public key cert based on the request
    $cert = $this->fetch_public_cert($request);

    // Pull the public key ID from the certificate
    $publickeyid = openssl_get_publickey($cert);

    // Check the computed signature against the one passed in the query
    $ok = openssl_verify($base_string, $decoded_sig, $publickeyid);

    // Release the key resource
    openssl_free_key($publickeyid);

    return $ok == 1;
  }
}

class OAuthRequest {
  private $parameters;
  private $http_method;
  private $http_url;
  // for debug purposes
  public $base_string;
  public static $version = '1.0';
  public static $POST_INPUT = 'php://input';

  function __construct($http_method, $http_url, $parameters=NULL) {
    @$parameters or $parameters = array();
    $parameters = array_merge( OAuthUtil::parse_parameters(parse_url($http_url, PHP_URL_QUERY)), $parameters);
    $this->parameters = $parameters;
    $this->http_method = $http_method;
    $this->http_url = $http_url;
  }

  /**
   * attempt to build up a request from what was passed to the server
   */
  public static function from_request($http_method=NULL, $http_url=NULL, $parameters=NULL) {
    $scheme = (!isset($_SERVER['HTTPS']) || $_SERVER['HTTPS'] != "on")
              ? 'http'
              : 'https';
    @$http_url or $http_url = $scheme .
                              '://' . $_SERVER['HTTP_HOST'] .
                              ':' .
                              $_SERVER['SERVER_PORT'] .
                              $_SERVER['REQUEST_URI'];
    @$http_method or $http_method = $_SERVER['REQUEST_METHOD'];

    // We weren't handed any parameters, so let's find the ones relevant to
    // this request.
    // If you run XML-RPC or similar you should use this to provide your own
    // parsed parameter-list
    if (!$parameters) {
      // Find request headers
      $request_headers = OAuthUtil::get_headers();

      // Parse the query-string to find GET parameters
      $parameters = OAuthUtil::parse_parameters($_SERVER['QUERY_STRING']);

      // It's a POST request of the proper content-type, so parse POST
      // parameters and add those overriding any duplicates from GET
      if ($http_method == "POST"
          && @strstr($request_headers["Content-Type"],
                     "application/x-www-form-urlencoded")
          ) {
        $post_data = OAuthUtil::parse_parameters(
          file_get_contents(self::$POST_INPUT)
        );
        $parameters = array_merge($parameters, $post_data);
      }

      // We have a Authorization-header with OAuth data. Parse the header
      // and add those overriding any duplicates from GET or POST
      if (@substr($request_headers['Authorization'], 0, 6) == "OAuth ") {
        $header_parameters = OAuthUtil::split_header(
          $request_headers['Authorization']
        );
        $parameters = array_merge($parameters, $header_parameters);
      }

    }

    return new OAuthRequest($http_method, $http_url, $parameters);
  }

  /**
   * pretty much a helper function to set up the request
   */
  public static function from_consumer_and_token($consumer, $token, $http_method, $http_url, $parameters=NULL) {
    @$parameters or $parameters = array();
    $defaults = array("oauth_version" => OAuthRequest::$version,
                      "oauth_nonce" => OAuthRequest::generate_nonce(),
                      "oauth_timestamp" => OAuthRequest::generate_timestamp(),
                      "oauth_consumer_key" => $consumer->key);
    if ($token)
      $defaults['oauth_token'] = $token->key;

    $parameters = array_merge($defaults, $parameters);

    return new OAuthRequest($http_method, $http_url, $parameters);
  }

  public function set_parameter($name, $value, $allow_duplicates = true) {
    if ($allow_duplicates && isset($this->parameters[$name])) {
      // We have already added parameter(s) with this name, so add to the list
      if (is_scalar($this->parameters[$name])) {
        // This is the first duplicate, so transform scalar (string)
        // into an array so we can add the duplicates
        $this->parameters[$name] = array($this->parameters[$name]);
      }

      $this->parameters[$name][] = $value;
    } else {
      $this->parameters[$name] = $value;
    }
  }

  public function get_parameter($name) {
    return isset($this->parameters[$name]) ? $this->parameters[$name] : null;
  }

  public function get_parameters() {
    return $this->parameters;
  }

  public function unset_parameter($name) {
    unset($this->parameters[$name]);
  }

  /**
   * The request parameters, sorted and concatenated into a normalized string.
   * @return string
   */
  public function get_signable_parameters() {
    // Grab all parameters
    $params = $this->parameters;

    // Remove oauth_signature if present
    // Ref: Spec: 9.1.1 ("The oauth_signature parameter MUST be excluded.")
    if (isset($params['oauth_signature'])) {
      unset($params['oauth_signature']);
    }

    return OAuthUtil::build_http_query($params);
  }

  /**
   * Returns the base string of this request
   *
   * The base string defined as the method, the url
   * and the parameters (normalized), each urlencoded
   * and the concated with &.
   */
  public function get_signature_base_string() {
    $parts = array(
      $this->get_normalized_http_method(),
      $this->get_normalized_http_url(),
      $this->get_signable_parameters()
    );

    $parts = OAuthUtil::urlencode_rfc3986($parts);

    return implode('&', $parts);
  }

  /**
   * just uppercases the http method
   */
  public function get_normalized_http_method() {
    return strtoupper($this->http_method);
  }

  /**
   * parses the url and rebuilds it to be
   * scheme://host/path
   */
  public function get_normalized_http_url() {
    $parts = parse_url($this->http_url);

    $port = @$parts['port'];
    $scheme = $parts['scheme'];
    $host = $parts['host'];
    $path = @$parts['path'];

    $port or $port = ($scheme == 'https') ? '443' : '80';

    if (($scheme == 'https' && $port != '443')
        || ($scheme == 'http' && $port != '80')) {
      $host = "$host:$port";
    }
    return "$scheme://$host$path";
  }

  /**
   * builds a url usable for a GET request
   */
  public function to_url() {
    $post_data = $this->to_postdata();
    $out = $this->get_normalized_http_url();
    if ($post_data) {
      $out .= '?'.$post_data;
    }
    return $out;
  }

  /**
   * builds the data one would send in a POST request
   */
  public function to_postdata() {
    return OAuthUtil::build_http_query($this->parameters);
  }

  /**
   * builds the Authorization: header
   */
  public function to_header($realm=null) {
	if($realm)
      $out = 'Authorization: OAuth realm="' . OAuthUtil::urlencode_rfc3986($realm) . '"';
    else
      $out = 'Authorization: OAuth';

    $total = array();
    foreach ($this->parameters as $k => $v) {
      if (substr($k, 0, 5) != "oauth") continue;
      if (is_array($v)) {
        throw new OAuthException('Arrays not supported in headers');
      }
      $out .= ',' .
              OAuthUtil::urlencode_rfc3986($k) .
              '="' .
              OAuthUtil::urlencode_rfc3986($v) .
              '"';
    }
    return $out;
  }

  public function __toString() {
    return $this->to_url();
  }

  public function sign_request($signature_method, $consumer, $token) {
    $this->set_parameter(
      "oauth_signature_method",
      $signature_method->get_name(),
      false
    );
    $signature = $this->build_signature($signature_method, $consumer, $token);
    $this->set_parameter("oauth_signature", $signature, false);
  }

  public function build_signature($signature_method, $consumer, $token) {
    $signature = $signature_method->build_signature($this, $consumer, $token);
    return $signature;
  }

  /**
   * util function: current timestamp
   */
  private static function generate_timestamp() {
    return time();
  }

  /**
   * util function: current nonce
   */
  private static function generate_nonce() {
    $mt = microtime();
    $rand = mt_rand();

    return md5($mt . $rand); // md5s look nicer than numbers
  }
}

class OAuthServer {
  protected $timestamp_threshold = 300; // in seconds, five minutes
  protected $version = '1.0';             // hi blaine
  protected $signature_methods = array();

  protected $data_store;

  function __construct($data_store) {
    $this->data_store = $data_store;
  }

  public function add_signature_method($signature_method) {
    $this->signature_methods[$signature_method->get_name()] =
      $signature_method;
  }

  // high level functions

  /**
   * process a request_token request
   * returns the request token on success
   */
  public function fetch_request_token(&$request) {
    $this->get_version($request);

    $consumer = $this->get_consumer($request);

    // no token required for the initial token request
    $token = NULL;

    $this->check_signature($request, $consumer, $token);

    // Rev A change
    $callback = $request->get_parameter('oauth_callback');
    $new_token = $this->data_store->new_request_token($consumer, $callback);

    return $new_token;
  }

  /**
   * process an access_token request
   * returns the access token on success
   */
  public function fetch_access_token(&$request) {
    $this->get_version($request);

    $consumer = $this->get_consumer($request);

    // requires authorized request token
    $token = $this->get_token($request, $consumer, "request");

    $this->check_signature($request, $consumer, $token);

    // Rev A change
    $verifier = $request->get_parameter('oauth_verifier');
    $new_token = $this->data_store->new_access_token($token, $consumer, $verifier);

    return $new_token;
  }

  /**
   * verify an api call, checks all the parameters
   */
  public function verify_request(&$request) {
    $this->get_version($request);
    $consumer = $this->get_consumer($request);
    $token = $this->get_token($request, $consumer, "access");
    $this->check_signature($request, $consumer, $token);
    return array($consumer, $token);
  }

  // Internals from here
  /**
   * version 1
   */
  private function get_version(&$request) {
    $version = $request->get_parameter("oauth_version");
    if (!$version) {
      // Service Providers MUST assume the protocol version to be 1.0 if this parameter is not present.
      // Chapter 7.0 ("Accessing Protected Ressources")
      $version = '1.0';
    }
    if ($version !== $this->version) {
      throw new OAuthException("OAuth version '$version' not supported");
    }
    return $version;
  }

  /**
   * figure out the signature with some defaults
   */
  private function get_signature_method(&$request) {
    $signature_method =
        @$request->get_parameter("oauth_signature_method");

    if (!$signature_method) {
      // According to chapter 7 ("Accessing Protected Ressources") the signature-method
      // parameter is required, and we can't just fallback to PLAINTEXT
      throw new OAuthException('No signature method parameter. This parameter is required');
    }

    if (!in_array($signature_method,
                  array_keys($this->signature_methods))) {
      throw new OAuthException(
        "Signature method '$signature_method' not supported " .
        "try one of the following: " .
        implode(", ", array_keys($this->signature_methods))
      );
    }
    return $this->signature_methods[$signature_method];
  }

  /**
   * try to find the consumer for the provided request's consumer key
   */
  private function get_consumer(&$request) {
    $consumer_key = @$request->get_parameter("oauth_consumer_key");
    if (!$consumer_key) {
      throw new OAuthException("Invalid consumer key");
    }

    $consumer = $this->data_store->lookup_consumer($consumer_key);
    if (!$consumer) {
      throw new OAuthException("Invalid consumer");
    }

    return $consumer;
  }

  /**
   * try to find the token for the provided request's token key
   */
  private function get_token(&$request, $consumer, $token_type="access") {
    $token_field = @$request->get_parameter('oauth_token');
    $token = $this->data_store->lookup_token(
      $consumer, $token_type, $token_field
    );
    if (!$token) {
      throw new OAuthException("Invalid $token_type token: $token_field");
    }
    return $token;
  }

  /**
   * all-in-one function to check the signature on a request
   * should guess the signature method appropriately
   */
  private function check_signature(&$request, $consumer, $token) {
    // this should probably be in a different method
    $timestamp = @$request->get_parameter('oauth_timestamp');
    $nonce = @$request->get_parameter('oauth_nonce');

    $this->check_timestamp($timestamp);
    $this->check_nonce($consumer, $token, $nonce, $timestamp);

    $signature_method = $this->get_signature_method($request);

    $signature = $request->get_parameter('oauth_signature');
    $valid_sig = $signature_method->check_signature(
      $request,
      $consumer,
      $token,
      $signature
    );

    if (!$valid_sig) {
      throw new OAuthException("Invalid signature");
    }
  }

  /**
   * check that the timestamp is new enough
   */
  private function check_timestamp($timestamp) {
    if( ! $timestamp )
      throw new OAuthException(
        'Missing timestamp parameter. The parameter is required'
      );

    // verify that timestamp is recentish
    $now = time();
    if (abs($now - $timestamp) > $this->timestamp_threshold) {
      throw new OAuthException(
        "Expired timestamp, yours $timestamp, ours $now"
      );
    }
  }

  /**
   * check that the nonce is not repeated
   */
  private function check_nonce($consumer, $token, $nonce, $timestamp) {
    if( ! $nonce )
      throw new OAuthException(
        'Missing nonce parameter. The parameter is required'
      );

    // verify that the nonce is uniqueish
    $found = $this->data_store->lookup_nonce(
      $consumer,
      $token,
      $nonce,
      $timestamp
    );
    if ($found) {
      throw new OAuthException("Nonce already used: $nonce");
    }
  }

}

class OAuthDataStore {
  function lookup_consumer($consumer_key) {
    // implement me
  }

  function lookup_token($consumer, $token_type, $token) {
    // implement me
  }

  function lookup_nonce($consumer, $token, $nonce, $timestamp) {
    // implement me
  }

  function new_request_token($consumer, $callback = null) {
    // return a new token attached to this consumer
  }

  function new_access_token($token, $consumer, $verifier = null) {
    // return a new access token attached to this consumer
    // for the user associated with this token if the request token
    // is authorized
    // should also invalidate the request token
  }

}

class OAuthUtil {
  public static function urlencode_rfc3986($input) {
  if (is_array($input)) {
    return array_map(array('OAuthUtil', 'urlencode_rfc3986'), $input);
  } else if (is_scalar($input)) {
    return str_replace(
      '+',
      ' ',
      str_replace('%7E', '~', rawurlencode($input))
    );
  } else {
    return '';
  }
}

  // This decode function isn't taking into consideration the above
  // modifications to the encoding process. However, this method doesn't
  // seem to be used anywhere so leaving it as is.
  public static function urldecode_rfc3986($string) {
    return urldecode($string);
  }

  // Utility function for turning the Authorization: header into
  // parameters, has to do some unescaping
  // Can filter out any non-oauth parameters if needed (default behaviour)
  public static function split_header($header, $only_allow_oauth_parameters = true) {
    $pattern = '/(([-_a-z]*)=("([^"]*)"|([^,]*)),?)/';
    $offset = 0;
    $params = array();
    while (preg_match($pattern, $header, $matches, PREG_OFFSET_CAPTURE, $offset) > 0) {
      $match = $matches[0];
      $header_name = $matches[2][0];
      $header_content = (isset($matches[5])) ? $matches[5][0] : $matches[4][0];
      if (preg_match('/^oauth_/', $header_name) || !$only_allow_oauth_parameters) {
        $params[$header_name] = OAuthUtil::urldecode_rfc3986($header_content);
      }
      $offset = $match[1] + strlen($match[0]);
    }

    if (isset($params['realm'])) {
      unset($params['realm']);
    }

    return $params;
  }

  // helper to try to sort out headers for people who aren't running apache
  public static function get_headers() {
    if (function_exists('apache_request_headers')) {
      // we need this to get the actual Authorization: header
      // because apache tends to tell us it doesn't exist
      $headers = apache_request_headers();

      // sanitize the output of apache_request_headers because
      // we always want the keys to be Cased-Like-This and arh()
      // returns the headers in the same case as they are in the
      // request
      $out = array();
      foreach( $headers AS $key => $value ) {
        $key = str_replace(
            " ",
            "-",
            ucwords(strtolower(str_replace("-", " ", $key)))
          );
        $out[$key] = $value;
      }
    } else {
      // otherwise we don't have apache and are just going to have to hope
      // that $_SERVER actually contains what we need
      $out = array();
      foreach ($_SERVER as $key => $value) {
        if (substr($key, 0, 5) == "HTTP_") {
          // this is chaos, basically it is just there to capitalize the first
          // letter of every word that is not an initial HTTP and strip HTTP
          // code from przemek
          $key = str_replace(
            " ",
            "-",
            ucwords(strtolower(str_replace("_", " ", substr($key, 5))))
          );
          $out[$key] = $value;
        }
      }
    }
    return $out;
  }

  // This function takes a input like a=b&a=c&d=e and returns the parsed
  // parameters like this
  // array('a' => array('b','c'), 'd' => 'e')
  public static function parse_parameters( $input ) {
    if (!isset($input) || !$input) return array();

    $pairs = explode('&', $input);

    $parsed_parameters = array();
    foreach ($pairs as $pair) {
      $split = explode('=', $pair, 2);
      $parameter = OAuthUtil::urldecode_rfc3986($split[0]);
      $value = isset($split[1]) ? OAuthUtil::urldecode_rfc3986($split[1]) : '';

      if (isset($parsed_parameters[$parameter])) {
        // We have already recieved parameter(s) with this name, so add to the list
        // of parameters with this name

        if (is_scalar($parsed_parameters[$parameter])) {
          // This is the first duplicate, so transform scalar (string) into an array
          // so we can add the duplicates
          $parsed_parameters[$parameter] = array($parsed_parameters[$parameter]);
        }

        $parsed_parameters[$parameter][] = $value;
      } else {
        $parsed_parameters[$parameter] = $value;
      }
    }
    return $parsed_parameters;
  }

  public static function build_http_query($params) {
    if (!$params) return '';

    // Urlencode both keys and values
    $keys = OAuthUtil::urlencode_rfc3986(array_keys($params));
    $values = OAuthUtil::urlencode_rfc3986(array_values($params));
    $params = array_combine($keys, $values);

    // Parameters are sorted by name, using lexicographical byte value ordering.
    // Ref: Spec: 9.1.1 (1)
    uksort($params, 'strcmp');

    $pairs = array();
    foreach ($params as $parameter => $value) {
      if (is_array($value)) {
        // If two or more parameters share the same name, they are sorted by their value
        // Ref: Spec: 9.1.1 (1)
        natsort($value);
        foreach ($value as $duplicate_value) {
          $pairs[] = $parameter . '=' . $duplicate_value;
        }
      } else {
        $pairs[] = $parameter . '=' . $value;
      }
    }
    // For each parameter, the name is separated from the corresponding value by an '=' character (ASCII code 61)
    // Each name-value pair is separated by an '&' character (ASCII code 38)
    return implode('&', $pairs);
  }
}

?>

And the basic version provided by Andy Smith at that time

<?php
require_once("OAuth.php");

class LinkedIn {
  public $base_url = "http://api.linkedin.com";
  public $secure_base_url = "https://api.linkedin.com";
  public $oauth_callback;
  public $consumer;
  public $request_token;
  public $access_token;
  public $oauth_verifier;
  public $signature_method;
  public $request_token_path;
  public $access_token_path;
  public $authorize_path;
  public $debug = false;

  function __construct($consumer_key, $consumer_secret, $oauth_callback = NULL) {

    if($oauth_callback) {
      $this->oauth_callback = $oauth_callback;
    }

    $this->consumer = new OAuthConsumer($consumer_key, $consumer_secret, $this->oauth_callback);
    $this->signature_method = new OAuthSignatureMethod_HMAC_SHA1();
    $this->request_token_path = $this->secure_base_url . "/uas/oauth/requestToken";
    $this->access_token_path = $this->secure_base_url . "/uas/oauth/accessToken";
    $this->authorize_path = $this->secure_base_url . "/uas/oauth/authorize";

  }

  function getRequestToken() {
    $consumer = $this->consumer;
    $request = OAuthRequest::from_consumer_and_token($consumer, NULL, "GET", $this->request_token_path);
    $request->set_parameter("oauth_callback", $this->oauth_callback);
    $request->sign_request($this->signature_method, $consumer, NULL);
    $headers = Array();
    $url = $request->to_url();
    $response = $this->httpRequest($url, $headers, "GET");
    parse_str($response, $response_params);
    $this->request_token = new OAuthConsumer($response_params['oauth_token'], $response_params['oauth_token_secret'], 1);
  }

  function generateAuthorizeUrl() {
    $consumer = $this->consumer;
    $request_token = $this->request_token;
    return $this->authorize_path . "?oauth_token=" . $request_token->key;
  }

  function getAccessToken($oauth_verifier) {
    $request = OAuthRequest::from_consumer_and_token($this->consumer, $this->request_token, "GET", $this->access_token_path);
    $request->set_parameter("oauth_verifier", $oauth_verifier);
    $request->sign_request($this->signature_method, $this->consumer, $this->request_token);
    $headers = Array();
    $url = $request->to_url();
    $response = $this->httpRequest($url, $headers, "GET");
    parse_str($response, $response_params);
    if($debug) {
      echo $response . "\n";
    }
    $this->access_token = new OAuthConsumer($response_params['oauth_token'], $response_params['oauth_token_secret'], 1);
  }

  function getProfile($resource = "~") {
    $profile_url = $this->base_url . "/v1/people/" . $resource;
    $request = OAuthRequest::from_consumer_and_token($this->consumer, $this->access_token, "GET", $profile_url);
    $request->sign_request($this->signature_method, $this->consumer, $this->access_token);
    $auth_header = $request->to_header("https://api.linkedin.com"); # this is the realm
    # This PHP library doesn't generate the header correctly when a realm is not specified.
    # Make sure there is a space and not a comma after OAuth
    // $auth_header = preg_replace("/Authorization\: OAuth\,/", "Authorization: OAuth ", $auth_header);
    // # Make sure there is a space between OAuth attribute
    // $auth_header = preg_replace('/\"\,/', '", ', $auth_header);
    if ($debug) {
      echo $auth_header;
    }
    // $response will now hold the XML document
    $response = $this->httpRequest($profile_url, $auth_header, "GET");
    return $response;
  }

  function setStatus($status) {
    $status_url = $this->base_url . "/v1/people/~/current-status";
    echo "Setting status...\n";
    $xml = "<current-status>" . htmlspecialchars($status, ENT_NOQUOTES, "UTF-8") . "</current-status>";
    echo $xml . "\n";
    $request = OAuthRequest::from_consumer_and_token($this->consumer, $this->access_token, "PUT", $status_url);
    $request->sign_request($this->signature_method, $this->consumer, $this->access_token);
    $auth_header = $request->to_header("https://api.linkedin.com");
    if ($debug) {
      echo $auth_header . "\n";
    }
    $response = $this->httpRequest($profile_url, $auth_header, "GET");
    return $response;
  }

  # Parameters should be a query string starting with "?"
  # Example search("?count=10&start=10&company=LinkedIn");
  function search($parameters) {
    $search_url = $this->base_url . "/v1/people-search:(people:(id,first-name,last-name,picture-url,site-standard-profile-request,headline),num-results)" . $parameters;
    //$search_url = $this->base_url . "/v1/people-search?keywords=facebook";

    echo "Performing search for: " . $parameters . "<br />";
    echo "Search URL: $search_url <br />";
    $request = OAuthRequest::from_consumer_and_token($this->consumer, $this->access_token, "GET", $search_url);
    $request->sign_request($this->signature_method, $this->consumer, $this->access_token);
    $auth_header = $request->to_header("https://api.linkedin.com");
    if ($debug) {
      echo $request->get_signature_base_string() . "\n";
      echo $auth_header . "\n";
    }
    $response = $this->httpRequest($search_url, $auth_header, "GET");
    return $response;
  }

  function httpRequest($url, $auth_header, $method, $body = NULL) {
    if (!$method) {
      $method = "GET";
    };

    $curl = curl_init();
    curl_setopt($curl, CURLOPT_URL, $url);
    curl_setopt($curl, CURLOPT_HEADER, 0);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($curl, CURLOPT_HTTPHEADER, array($auth_header)); // Set the headers.

    if ($body) {
      curl_setopt($curl, CURLOPT_POST, 1);
      curl_setopt($curl, CURLOPT_POSTFIELDS, $body);
      curl_setopt($curl, CURLOPT_CUSTOMREQUEST, $method);
      curl_setopt($curl, CURLOPT_HTTPHEADER, array($auth_header, "Content-Type: text/xml;charset=utf-8"));
    }

    $data = curl_exec($curl);
    if ($this->debug) {
      echo $data . "\n";
    }
    curl_close($curl);
    return $data;
  }

}

In my project I updated linkedin.php by adding several functions, so now I’m mentioning those functions here.

1. Search Professionals based on location, industry, company name:

It may be very important for your site to search some professionals via linkedin. To understand the full reference of linkedin search visit their documentation . Based on this documentation I created a method in linkedin.php that solves my requirement


  function search($parameters) {
    $search_url = $this->base_url . "/v1/people-search:(people:(id,first-name,last-name,picture-url,site-standard-profile-request,headline),num-results)" . $parameters . "&facets=location,industry&facet=location,us:0&facet=industry,4";
    $request = OAuthRequest::from_consumer_and_token($this->consumer, $this->access_token, "GET", $search_url);
    $request->sign_request($this->signature_method, $this->consumer, $this->access_token);
    $auth_header = $request->to_header("https://api.linkedin.com");
    if ($debug) {
      echo $request->get_signature_base_string() . "\n";
      echo $auth_header . "\n";
    }
    $response = $this->httpRequest($search_url, $auth_header, "GET");
    return $response;
  }

And from other page i just call them:

$keyword            =  "Facebook";
$searchParam        =   "company-name={$keyword}&current-company=true&start=0&count=25&sort=distance";
$search_response    =   $linkedin->search("?$searchParam");

So here the search function searches professional’s linkedin id, first name, last name, ……. based on the company name that i provided during function call and also those people work those companies currently

current-company=true

and those people must be in located in US

facet=location,us

and those people must be Computer Software Industry related.

facet=industry,4

For industry code checkout this. So you can easily use my function and modify so that it meets your requirement.

2. After searching people send them message via linkedin user id

This was another task for me. After user found some professionals they could send them message. Here you’ll find linkedin documentation based on that I created another method.

function sendMessageById($id, $ccUser=FALSE, $subject='', $message='') {
      $messageUrl   =   $this->base_url . "/v1/people/~/mailbox";

      $subject      =   htmlspecialchars($subject, ENT_NOQUOTES, "UTF-8") ;
      $message      =   htmlspecialchars($message, ENT_NOQUOTES, "UTF-8") ;

      if ($ccUser){
          $CCToUser   =   "<recipient>
                             <person path='/people/~'/>
                           </recipient>";
      }
      else{
          $CCToUser   =   '';
      }

      $xml = "<mailbox-item>
                <recipients>
                    $CCToUser
                    <recipient>
                        <person path='/people/$id' />
                    </recipient>
                </recipients>
                <subject>$subject</subject>
                <body>$message</body>
              </mailbox-item>";

      //echo $xml . "\n";
      $request = OAuthRequest::from_consumer_and_token($this->consumer, $this->access_token, "POST", $messageUrl);
      $request->sign_request($this->signature_method, $this->consumer, $this->access_token);
      $auth_header = $request->to_header("https://api.linkedin.com");
      if ($debug) {
          echo $auth_header . "\n";
      }
      $response = $this->httpRequest($messageUrl, $auth_header, "POST", $xml);
      return $response;
  }

Here $id is the other user linkedin id, $ccUser=FALSE means no CC message to the sender user, if you pass TRUE it will send the same message to the sender user also.

To call this method use the following way:

$apiCallStatus      =   $linkedin->sendMessageById($targetUser, FALSE, $subject, $message);

if (empty($apiCallStatus)){
       echo "Message sent successfully!";
}
else{
       $apiXMLResponse =   simplexml_load_string($apiCallStatus);
       echo "<pre>";
       print_r($apiXMLResponse);
       echo "</pre>";
}

3. After searching people invite them to be connected via linkedin user ID

Checkout the linkedin Invitation API reference for more information.

function sendInvitationById($id, $authkey, $subject='', $message='') {
      $messageUrl   =   $this->base_url . "/v1/people/~/mailbox";

      $subject      =   htmlspecialchars($subject, ENT_NOQUOTES, "UTF-8") ;
      $message      =   htmlspecialchars($message, ENT_NOQUOTES, "UTF-8") ;

      $xml = "<mailbox-item>
              <recipients>
                <recipient>
                  <person path='/people/id=$id' />
                </recipient>
              </recipients>
              <subject>$subject</subject>
              <body>$message</body>
              <item-content>
                <invitation-request>
                  <connect-type>friend</connect-type>
                  <authorization>
                    <name>NAME_SEARCH</name>
                    <value>$authkey</value>
                  </authorization>
                </invitation-request>
              </item-content>
            </mailbox-item>";

      $request = OAuthRequest::from_consumer_and_token($this->consumer, $this->access_token, "POST", $messageUrl);
      $request->sign_request($this->signature_method, $this->consumer, $this->access_token);
      $auth_header = $request->to_header("https://api.linkedin.com");
      if ($debug) {
          echo $xml . "\n";
          echo $auth_header . "\n";
      }
      $response = $this->httpRequest($messageUrl, $auth_header, "POST", $xml);
      return $response;
  }

Its very important to know that, after you found people you have to retrieve their ID and authkey, otherwise you can’t send invitation them via ID.

So call the method using the following way:

$apiCallStatus      =   $linkedin->sendInvitationById($targetUser, $authKey, $subject, $message);

if (empty($apiCallStatus)){
   echo "Invitation sent successfully!";
}
else{
   $apiXMLResponse =   simplexml_load_string($apiCallStatus);
   echo '<pre>';
   print_r($apiXMLResponse);
   echo '</pre>';
}

4. Send invitation via Email:

function sendInvitationByEmail($firstName, $lastName, $email, $subject='', $message='') {
      $messageUrl   =   $this->base_url . "/v1/people/~/mailbox";

      $subject      =   htmlspecialchars($subject, ENT_NOQUOTES, "UTF-8") ;
      $message      =   htmlspecialchars($message, ENT_NOQUOTES, "UTF-8") ;

      $xml = "<mailbox-item>
              <recipients>
                <recipient>
                  <person path='/people/email=$email'>
                    <first-name>$firstName</first-name>
                    <last-name>$lastName</last-name>
                  </person>
                </recipient>
              </recipients>
              <subject>$subject</subject>
              <body>Please join my professional network on LinkedIn.</body>
              <item-content>
                <invitation-request>
                  <connect-type>friend</connect-type>
                </invitation-request>
              </item-content>
            </mailbox-item>";

      $request = OAuthRequest::from_consumer_and_token($this->consumer, $this->access_token, "POST", $messageUrl);
      $request->sign_request($this->signature_method, $this->consumer, $this->access_token);
      $auth_header = $request->to_header("https://api.linkedin.com");
      if ($debug) {
          echo $xml . "\n";
          echo $auth_header . "\n";
      }
      $response = $this->httpRequest($messageUrl, $auth_header, "POST", $xml);
      return $response;
  }

Sometimes linkedin restricted some user accounts so that they can’t send invitation to other users via linkedin id, they have to provide email address to make connection. So in this case you use the following function to send invitation. Just call it

$apiCallStatus      =   $linkedin->sendInvitationByEmail($firstName, $lastName, $email, $subject, $message);
if (empty($apiCallStatus)){
   echo "Invitation sent successfully!";
}
else{
   $apiXMLResponse =   simplexml_load_string($apiCallStatus);
   echo '<pre>';
   print_r($apiXMLResponse);
   echo '</pre>';
}

5. Share something in linkedin

If you want to share a photo, link and some comment with title then use this function. Checkout linkedin API Reference to understand fully about the API.

function share($comment, $title, $url, $imageUrl) {
      $shareUrl     =   $this->base_url . "/v1/people/~/shares";

      $xml = "<share>
              <comment>$comment</comment>
              <content>
                 <title>$title</title>
                 <submitted-url>$url</submitted-url>
                 <submitted-image-url>$imageUrl</submitted-image-url>
              </content>
              <visibility>
                 <code>anyone</code>
              </visibility>
            </share>";

      $request = OAuthRequest::from_consumer_and_token($this->consumer, $this->access_token, "POST", $shareUrl);
      $request->sign_request($this->signature_method, $this->consumer, $this->access_token);
      $auth_header = $request->to_header("https://api.linkedin.com");
      if ($debug) {
          echo $xml . "\n";
          echo $auth_header . "\n";
      }
      $response = $this->httpRequest($shareUrl, $auth_header, "POST", $xml);
      return $response;
  }

So you can easily call them by

            $apiCallStatus    =   $linkedin->share($comment, $title, $targetUrl, $imgUrl);
            $apiXMLResponse   =   simplexml_load_string($apiCallStatus);
            if (empty($apiXMLResponse)){
                echo "You successfully shared it in linkedin";
            }
            else{
                echo "Unknown error! Please try again!";
                echo '<pre>';
                print_r($apiXMLResponse);
                echo '</pre>';
            }

I added these methods and thought this might be help you to solve similar requirements for your web application.

About mahmud ahsan

Founder And Lead Programmer at iThinkdiff.net

, , , , , ,

26 Responses to Integrate linkedin API part 2

  1. hasan November 13, 2010 at 12:56 am #

    Nice article. I have been trying for several days to login to the linkedin site using php curl but with no luck. I can get past google,yahoo but not linedin!!!!

    Do you think it’s possible to login at linkedin using php curl?

    I searched google, went through almost all search pages. Nobody hasn’t published an article on this!

    As linkedin has limited api call limit basic php curl would be a better approach for pulling a large amount of data.
    what do you think?

    • website May 17, 2013 at 5:45 am #

      Greate post. Keep writing such kind of information on your page.
      Im really impressed by your site.
      Hello there, You’ve done an incredible job. I’ll certainly digg it and individually recommend to
      my friends. I am sure they will be benefited from this website.

    • Christina May 17, 2013 at 5:50 am #

      magnificent submit, very informative. I’m wondering why the other specialists of this sector do not notice this. You must continue your writing. I’m sure,
      you have a huge readers’ base already!

  2. Nishant Shrivastava January 3, 2011 at 7:13 pm #

    Hello Mahmud,
    I have been digging my head in the API you provided and the oAuth authentication with the LinkedIn Api,but I really can’t understand why the request token remains blank!

    I tried debugging it and found out that in the function getRequestToken , $response remains blank that’s why when my application redirects to authenticate from the LinkedIn it gives me this error :
    We were unable to find the authorization token

    Can you please guide me how can I solve this thing or the stuff which I must be missing out..?

    P.S : I am testing the whole code in my local system and have set up a virtual domain(e.g http://localhost.test.com/) for this.And the server is Apache on windows environment.

    Thanks in advance
    Nishant Shrivastava

    • devjohn April 3, 2012 at 12:46 pm #

      Add this in your linkedin.php

      curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, FALSE);
      curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 2);

  3. Jaikar January 17, 2011 at 10:37 pm #

    Nishant, i think you need to install the oAuth extension for php on the local machine to receive the request token. i dont think oauth extension is available for windows, but you can compile for the linux. it will work if you upload the code to the hosting server.

  4. Arif Amir January 29, 2011 at 1:01 pm #

    Dear Sir:

    I am working on the LinkedIn app for my university. which will get the alumni data to our university database so that we have access to the latest profiles of our alumni.

    Well I found your tutorials very helpful. but I am facing a problem. Whenever I try to create the new app in LinkedIn it shows the following error when I submit the form.

    “There was an unexpected problem that prevented us from completing your request.

    Can you help me to how to solve this problem.

    –Regards–
    Muhammad Arif Amir
    Islamabad
    Pakistan

    • mahmud ahsan January 30, 2011 at 8:15 pm #

      Hello Arif, your problem is when you try to create application in linkedin it shows error. I don’t know why this is happening :S

  5. tech February 13, 2011 at 1:10 pm #

    Nice. very good article.. useful one.

  6. Yasir February 18, 2011 at 9:35 am #

    Hi,
    Thank you very useful. I tried you use this code in wordpress everything goes fine but when linkedin redirect to demo.php in wordpress it does not display profile and in address bar I see something like “http://yasir.com/demo.php/?oauth_token=0b4155bf-2c4b-495b-bd32-1e9b33f52c7f&oauth_verifier=73065″
    Wordpress adding slash here so it does not work in wordpress. Please could anyone tell me what I need to do to make it work in wordpress. And please also help me to how I will just display firstname, lastname and company from the xml return array i don’t wanna display xml code like in demo.php.
    Please help me out.

  7. Pavan March 23, 2011 at 4:39 pm #

    Hello All,

    Best article i have seen till now on linkedin API.
    I am using http://thinkdiff.net/linkedin/integrate-linkedin-api-in-your-site/ api.
    But am not getting oauth_token.
    I am getting this blank.
    Can anybody tell me, what happen here.
    Am i doing worng?

    Authorization URL: https://api.linkedin.com/uas/oauth/authorize?oauth_token=

    • Jack Manlosa September 8, 2011 at 6:47 pm #

      Hi Pavan,

      it’s got something to do with your server verifying SSL certificates between the HOST and the PEER.

      so what you will have to do is to modify linkedin.php and add this code to the CURL process, in line 166 function httpRequest:

      curl_setopt (CURLOPT_SSL_VERIFYHOST,0);
      curl_setopt (CURLOPT_SSL_VERIFYPEER,0);

      that should solved it.

      the reason for that is that curl quits if it can’t verify the ssl certificate leaving you with blank header return, which gives you a blank token.

      -jack

  8. Mukul April 26, 2011 at 12:01 am #

    I’ve integrated linkedin signin into my site…. once a user logs in… is there an easy way to get a count of the number of connections he/she has?

  9. Xahyd June 14, 2011 at 3:28 pm #

    i got these two error notice about debug variable:

    Notice: Undefined variable: debug in D:\wamp\www\test\linkedinoauth\linkedin.php on line 74
    Notice: Undefined variable: debug in D:\wamp\www\test\linkedinoauth\linkedin.php on line 124

    any help???

  10. dipen patel June 17, 2011 at 12:38 pm #

    gice example of search company and send mail and invitation….

  11. dipen patel June 17, 2011 at 3:16 pm #

    403 1308302139130 TBGUV7JLV8 0 People search must be done on behalf of a member.
    this type of data how to gentrate company profile form the output after calling search function in linkedin.php

  12. dipen patel June 18, 2011 at 4:29 pm #

    give a full example of search people or company…also give a code for that.
    i m waitong for your replay,,,,

  13. Arsalan March 20, 2012 at 6:09 am #

    What about getting Contacts CSV?

  14. Kasun June 25, 2012 at 11:35 am #

    Thanks man i’ve been looking for this everywhere. u are a time saver..

  15. siva July 6, 2012 at 1:36 pm #

    @mahmud ahsan
    thank you for putting up this code i have designed an app that get the users contact list by using your code but when iam trying to implement send message its telling me
    “Access to messages denied” i there any need to get extend permissions to send mail iam using localhost or ip. does it work if we create a virtualhost like dev.name.com/

    • siva July 6, 2012 at 3:52 pm #

      its working fine

  16. lucas July 26, 2012 at 1:55 am #

    is the send invitation working correctly ?

  17. damien March 16, 2013 at 4:10 pm #

    Hey Everyone,

    In order to get more authorisations from the user (like network acess etc..)

    you need to change getRequestToken() in the linkedin.php file.

    function getRequestToken()
    	{
    		$consumer = $this->consumer;
    		$request = OAuthRequest::from_consumer_and_token($consumer, NULL, "GET", $this->request_token_path);
    		$request->set_parameter("oauth_callback", $this->oauth_callback);
    		$request->set_parameter("scope", 'rw_nus');
    		$request->sign_request($this->signature_method, $consumer, NULL);
    		$headers = Array();
    		$url = $request->to_url();
    		$response = $this->httpRequest($url, $headers, "GET");
    		parse_str($response, $response_params);
    		$this->request_token = new OAuthConsumer($response_params['oauth_token'], $response_params['oauth_token_secret'], 1);
    	}
    

    I added $request->set_parameter(“scope”, ‘rw_nus’); which asks the user access to network.

    For other acces parameters, see : http://developer.linkedin.com/documents/authentication#granting

    @++

    damien

  18. Abdul July 19, 2013 at 1:45 pm #

    hi.. sir our article is nice i.m a fresher so getting this error after running our code and also please specify where to put requestToken oauth_verifier in code

    it ll be glad if u help………

    ( ! ) SCREAM: Error suppression ignored for
    ( ! ) Notice: Undefined index: requestToken in C:\wamp\www\linkedin\demo.php on line 28
    Call Stack
    # Time Memory Function Location
    1 0.0020 147112 {main}( ) ..\demo.php:0

    ( ! ) SCREAM: Error suppression ignored for
    ( ! ) Notice: Undefined index: oauth_verifier in C:\wamp\www\linkedin\demo.php on line 29
    Call Stack
    # Time Memory Function Location
    1 0.0020 147112 {main}( ) ..\demo.php:0

    ( ! ) SCREAM: Error suppression ignored for
    ( ! ) Notice: Undefined index: oauth_access_token in C:\wamp\www\linkedin\demo.php on line 30
    Call Stack
    # Time Memory Function Location
    1 0.0020 147112 {main}( ) ..\demo.php:0
    My Profile Info

    404
    1374219118725
    VHDCVEWSNN
    0
    Could not find person based on: ~

    Performing search for: ?company-name=facebook&count=10
    Search URL: http://api.linkedin.com/v1/people-search:(people:(id,first-name,last-name,picture-url,site-standard-profile-request,headline),num-results)?company-name=facebook&count=10
    Look people who worked in facebookSimpleXMLElement Object
    (
    [status] => 403
    [timestamp] => 1374219119966
    [request-id] => 9UK8VI6998
    [error-code] => 0
    [message] => People search must be done on behalf of a member.
    )

  19. Sohel September 16, 2013 at 1:00 pm #

    Hi I am getting

    401
    1379314562154
    J9JL1CV8F0
    0
    [unauthorized]. OAU:t33ono3aiqtd|*01|*01|*01:1379314562:eQ8kiuvZfNYwiSdZnltocEYRdM0=

    for getConnection()

    Any idea, please its urgent

  20. Naved October 18, 2013 at 7:20 pm #

    i implemented your code to send message to the connections
    but i got this error..

    403
    1382101291707
    NC1DM5NO3T
    0
    Can’t access another member’s mailbox

    any solution for this?