Location: PHPKode > scripts > Flattr - WordPress plugin > flattr/oAuth/oauth.php
<?php

/* Generic exception class
 */

if(!class_exists('OAuthConsumer')) {
    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]";
      }
    }
}

if(!class_exists('OAuthToken')) {
    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
 */
if(!class_exists('OAuthSignatureMethod')) {
    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")
 */

if(!class_exists('OAuthSignatureMethod_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")
 */
if(!class_exists('OAuthSignatureMethod_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")
 */
if (!class_exists('OAuthSignatureMethod_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;
      }
    }
}

if(!class_exists(('OAuthRequest'))) {
    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) {
        $first = true;
            if($realm) {
          $out = 'Authorization: OAuth realm="' . OAuthUtil::urlencode_rfc3986($realm) . '"';
          $first = false;
        } 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 Exception('Arrays not supported in headers');
          }
          $out .= ($first) ? ' ' : ',';
          $out .= OAuthUtil::urlencode_rfc3986($k) .
                  '="' .
                  OAuthUtil::urlencode_rfc3986($v) .
                  '"';
          $first = false;
        }
        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
      }
    }
}

if (!class_exists('OAuthServer')) {
    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 !== $this->version) {
          throw new Exception("OAuth version '$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 Exception('No signature method parameter. This parameter is required');
        }

        if (!in_array($signature_method,
                      array_keys($this->signature_methods))) {
          throw new Exception(
            "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 Exception("Invalid consumer key");
        }

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

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

        // verify that timestamp is recentish
        $now = time();
        if (abs($now - $timestamp) > $this->timestamp_threshold) {
          throw new Exception(
            "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 Exception(
            '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 Exception("Nonce already used: $nonce");
        }
      }

    }
}

if (!class_exists('OAuthDataStore')) {
    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
      }

    }
}

if (!class_exists('OAuthUtil')) {
    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)
      // May 28th, 2010 - method updated to tjerk.meesters for a speed improvement.
      //                  see http://code.google.com/p/oauth/issues/detail?id=163
      public static function split_header($header, $only_allow_oauth_parameters = true) {
        $params = array();
        if (preg_match_all('/('.($only_allow_oauth_parameters ? 'oauth_' : '').'[a-z_-]*)=(:?"([^"]*)"|([^,]*))/', $header, $matches)) {
          foreach ($matches[1] as $i => $h) {
            $params[$h] = OAuthUtil::urldecode_rfc3986(empty($matches[3][$i]) ? $matches[4][$i] : $matches[3][$i]);
          }
          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
          $out = array();
          if( isset($_SERVER['CONTENT_TYPE']) )
            $out['Content-Type'] = $_SERVER['CONTENT_TYPE'];
          if( isset($_ENV['CONTENT_TYPE']) )
            $out['Content-Type'] = $_ENV['CONTENT_TYPE'];

          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);
      }

    }
}
Return current item: Flattr - WordPress plugin