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Long Term Support Release

  • Bug fixes for general core bugs in 3.9.x will end* 10 May 2021 (12 months).
  • Bug fixes for security issues in 3.9.x will end* 8 May 2023 (36 months).
  • PHP version: minimum PHP 7.2.0 Note: minimum PHP version has increased since Moodle 3.8. PHP 7.3.x and 7.4.x are supported too.
/mod/lti/ -> OAuth.php (source)
<?php
// This file is part of BasicLTI4Moodle
//
// BasicLTI4Moodle is an IMS BasicLTI (Basic Learning Tools for Interoperability)
// consumer for Moodle 1.9 and Moodle 2.0. BasicLTI is a IMS Standard that allows web
// based learning tools to be easily integrated in LMS as native ones. The IMS BasicLTI
// specification is part of the IMS standard Common Cartridge 1.1 Sakai and other main LMS
// are already supporting or going to support BasicLTI. This project Implements the consumer
// for Moodle. Moodle is a Free Open source Learning Management System by Martin Dougiamas.
// BasicLTI4Moodle is a project iniciated and leaded by Ludo(Marc Alier) and Jordi Piguillem
// at the GESSI research group at UPC.
// SimpleLTI consumer for Moodle is an implementation of the early specification of LTI
// by Charles Severance (Dr Chuck) htp://dr-chuck.com , developed by Jordi Piguillem in a
// Google Summer of Code 2008 project co-mentored by Charles Severance and Marc Alier.
//
// BasicLTI4Moodle is copyright 2009 by Marc Alier Forment, Jordi Piguillem and Nikolas Galanis
// of the Universitat Politecnica de Catalunya http://www.upc.edu
// Contact info: Marc Alier Forment granludo @ gmail.com or marc.alier @ upc.edu
//
// OAuth.php is distributed under the MIT License
//
// The MIT License
//
// Copyright (c) 2007 Andy Smith
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.

> /** namespace moodle\mod\lti;//Using a namespace as the basicLTI module imports classes with the same names > * This file contains the OAuth 1.0a implementation used for support for LTI 1.1. > * defined('MOODLE_INTERNAL') || die; > * @package mod_lti > * @copyright moodle $oauth_last_computed_signature = false; > * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later > */
< $oauth_last_computed_signature = false;
> $lastcomputedsignature = false;
< /* Generic exception class
> /** > * Generic exception class
class OAuthException extends \Exception { // pass }
> /** class OAuthConsumer { > * OAuth 1.0 Consumer class public $key; > */
public $secret;
> /** @var string|null callback URL. */ function __construct($key, $secret, $callback_url = null) { > public ?string $callback_url; $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 $this->to_string(); } } class OAuthSignatureMethod { public function check_signature(&$request, $consumer, $token, $signature) { $built = $this->build_signature($request, $consumer, $token); return $built == $signature; } }
< class OAuthSignatureMethod_HMAC_SHA1 extends OAuthSignatureMethod { < function get_name() { < return "HMAC-SHA1"; < }
> > /** > * Base class for the HMac based signature methods. > */ > abstract class OAuthSignatureMethod_HMAC extends OAuthSignatureMethod { > > /** > * Name of the Algorithm used. > * > * @return string algorithm name. > */ > abstract public function get_name(): string;
public function build_signature($request, $consumer, $token) {
< global $oauth_last_computed_signature; < $oauth_last_computed_signature = false;
> global $lastcomputedsignature; > $lastcomputedsignature = false;
< $base_string = $request->get_signature_base_string(); < $request->base_string = $base_string;
> $basestring = $request->get_signature_base_string(); > $request->base_string = $basestring;
$key_parts = array( $consumer->secret, ($token) ? $token->secret : "" ); $key_parts = OAuthUtil::urlencode_rfc3986($key_parts); $key = implode('&', $key_parts);
< $computed_signature = base64_encode(hash_hmac('sha1', $base_string, $key, true)); < $oauth_last_computed_signature = $computed_signature; < return $computed_signature;
> $computedsignature = base64_encode(hash_hmac(strtolower(substr($this->get_name(), 5)), $basestring, $key, true)); > $lastcomputedsignature = $computedsignature; > return $computedsignature; > } > > } > > /** > * Implementation for SHA 1. > */ > class OAuthSignatureMethod_HMAC_SHA1 extends OAuthSignatureMethod_HMAC { > /** > * Name of the Algorithm used. > * > * @return string algorithm name. > */ > public function get_name(): string { > return "HMAC-SHA1"; > }
}
> /** } > * Implementation for SHA 256. > */ class OAuthSignatureMethod_PLAINTEXT extends OAuthSignatureMethod { > class OAuthSignatureMethod_HMAC_SHA256 extends OAuthSignatureMethod_HMAC { public function get_name() { > /** return "PLAINTEXT"; > * Name of the Algorithm used. } > * > * @return string algorithm name. public function build_signature($request, $consumer, $token) { > */ $sig = array( > public function get_name(): string { OAuthUtil::urlencode_rfc3986($consumer->secret) > return "HMAC-SHA256"; ); > }
< public function get_name() {
> /** > * Name of the Algorithm used. > * > * @return string algorithm name. > */ > public function get_name(): string {
if ($token) { array_push($sig, OAuthUtil::urlencode_rfc3986($token->secret)); } else { array_push($sig, ''); } $raw = implode("&", $sig); // for debug purposes $request->base_string = $raw; return OAuthUtil::urlencode_rfc3986($raw); } } class OAuthSignatureMethod_RSA_SHA1 extends OAuthSignatureMethod {
< public function get_name() {
> /** > * Name of the Algorithm used. > * > * @return string algorithm name. > */ > public function get_name(): string {
return "RSA-SHA1"; } protected function fetch_public_cert(&$request) { // not implemented yet, ideas are: // (1) do a lookup in a table of trusted certs keyed off of consumer // (2) fetch via http using a url provided by the requester // (3) some sort of specific discovery code based on request // // either way should return a string representation of the certificate throw new OAuthException("fetch_public_cert not implemented"); } protected function fetch_private_cert(&$request) { // not implemented yet, 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 throw new OAuthException("fetch_private_cert not implemented"); } 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, $privatekeyid);
> // Avoid passing null values to base64_encode. // Release the key resource > if (!$ok) { openssl_free_key($privatekeyid); > throw new OAuthException("OpenSSL unable to sign data"); > } return base64_encode($signature); > } > // TODO: Remove this block once PHP 8.0 becomes required. > if (PHP_MAJOR_VERSION < 8) {
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, $publickeyid);
> // TODO: Remove this block once PHP 8.0 becomes required. // Release the key resource > if (PHP_MAJOR_VERSION < 8) {
openssl_free_key($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(); $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 = (!is_https()) ? 'http' : 'https'; $port = ""; if ($_SERVER['SERVER_PORT'] != "80" && $_SERVER['SERVER_PORT'] != "443" && strpos(':', $_SERVER['HTTP_HOST']) < 0) { $port = ':' . $_SERVER['SERVER_PORT']; } @$http_url or $http_url = $scheme . '://' . $_SERVER['HTTP_HOST'] . $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']); $ourpost = $_POST; // Add POST Parameters if they exist $parameters = array_merge($parameters, $ourpost); // We have a Authorization-header with OAuth data. Parse the header // and add those overriding any duplicates from GET or POST if (@substr($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(); $defaults = array( "oauth_version" => self::$version, "oauth_nonce" => self::generate_nonce(), "oauth_timestamp" => self::generate_timestamp(), "oauth_consumer_key" => $consumer->key ); if ($token) { $defaults['oauth_token'] = $token->key; } $parameters = array_merge($defaults, $parameters); // Parse the query-string to find and add GET parameters $parts = parse_url($http_url); if (isset($parts['query'])) { $qparms = OAuthUtil::parse_parameters($parts['query']); $parameters = array_merge($qparms, $parameters); } return new OAuthRequest($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
> * Parses {@see http_url} and returns normalized scheme://host/path if non-empty, otherwise return empty string > * > * @return string
*/ public function get_normalized_http_url() {
> if ($this->http_url === '') { $parts = parse_url($this->http_url); > return ''; > } $port = @$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() { $out = 'Authorization: OAuth realm=""'; $total = array(); foreach ($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); $new_token = $this->data_store->new_request_token($consumer); 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); $new_token = $this->data_store->new_access_token($token, $consumer); return $new_token; } /** * verify an api call, checks all the parameters */ public function verify_request(&$request) {
< global $oauth_last_computed_signature; < $oauth_last_computed_signature = false;
> global $lastcomputedsignature; > $lastcomputedsignature = false;
$this->get_version($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) { $version = 1.0; } if ($version && $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) { $signature_method = "PLAINTEXT"; } if (!in_array($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 = @ $request->get_parameter('oauth_token'); if (!$token_field) { return false; } $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
< global $oauth_last_computed_signature; < $oauth_last_computed_signature = false;
> global $lastcomputedsignature; > $lastcomputedsignature = false;
$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) { $ex_text = "Invalid signature";
< if ($oauth_last_computed_signature) { < $ex_text = $ex_text . " ours= $oauth_last_computed_signature yours=$signature";
> if ($lastcomputedsignature) { > $ex_text = $ex_text . " ours= $lastcomputedsignature yours=$signature";
} throw new OAuthException($ex_text); } } /** * check that the timestamp is new enough */ private function check_timestamp($timestamp) { // verify that timestamp is recentish $now = time(); if ($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) { // 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) { // return a new token attached to this consumer } function new_access_token($token, $consumer) { // return a new access token attached to this consumer // for the user associated with this token if the request token // is authorized // should also invalidate the request token } } class OAuthUtil { public static function urlencode_rfc3986($input) { if (is_array($input)) { return array_map(array( 'moodle\mod\lti\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] = self::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 $in = apache_request_headers(); $out = array(); foreach ($in as $key => $value) { $key = str_replace(" ", "-", ucwords(strtolower(str_replace("-", " ", $key)))); $out[$key] = $value; } return $out; } // 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); $parameter = self::urldecode_rfc3986($split[0]); $value = isset($split[1]) ? self::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 $keys = self::urlencode_rfc3986(array_keys($params)); $values = self::urlencode_rfc3986(array_values($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); } }