WordPress/wp-includes/http.php

<?php
/**
 * Simple and uniform HTTP request API.
 *
 * Will eventually replace and standardize the WordPress HTTP requests made.
 *
 * @link http://trac.wordpress.org/ticket/4779 HTTP API Proposal
 *
 * @package WordPress
 * @subpackage HTTP
 * @since 2.7.0
 */

/**
 * Returns the initialized WP_Http Object
 *
 * @since 2.7.0
 * @access private
 *
 * @return WP_Http HTTP Transport object.
 */
function &_wp_http_get_object() {
	static $http;

	if ( is_null($http) )
		$http = new WP_Http();

	return $http;
}

/**
 * Retrieve the raw response from the HTTP request.
 *
 * The array structure is a little complex.
 *
 * <code>
 * $res = array( 'headers' => array(), 'response' => array('code' => int, 'message' => string) );
 * </code>
 *
 * All of the headers in $res['headers'] are with the name as the key and the
 * value as the value. So to get the User-Agent, you would do the following.
 *
 * <code>
 * $user_agent = $res['headers']['user-agent'];
 * </code>
 *
 * The body is the raw response content and can be retrieved from $res['body'].
 *
 * This function is called first to make the request and there are other API
 * functions to abstract out the above convoluted setup.
 *
 * @since 2.7.0
 *
 * @param string $url Site URL to retrieve.
 * @param array $args Optional. Override the defaults.
 * @return WP_Error|array The response or WP_Error on failure.
 */
function wp_remote_request($url, $args = array()) {
	$objFetchSite = _wp_http_get_object();
	return $objFetchSite->request($url, $args);
}

/**
 * Retrieve the raw response from the HTTP request using the GET method.
 *
 * @see wp_remote_request() For more information on the response array format.
 *
 * @since 2.7.0
 *
 * @param string $url Site URL to retrieve.
 * @param array $args Optional. Override the defaults.
 * @return WP_Error|array The response or WP_Error on failure.
 */
function wp_remote_get($url, $args = array()) {
	$objFetchSite = _wp_http_get_object();
	return $objFetchSite->get($url, $args);
}

/**
 * Retrieve the raw response from the HTTP request using the POST method.
 *
 * @see wp_remote_request() For more information on the response array format.
 *
 * @since 2.7.0
 *
 * @param string $url Site URL to retrieve.
 * @param array $args Optional. Override the defaults.
 * @return WP_Error|array The response or WP_Error on failure.
 */
function wp_remote_post($url, $args = array()) {
	$objFetchSite = _wp_http_get_object();
	return $objFetchSite->post($url, $args);
}

/**
 * Retrieve the raw response from the HTTP request using the HEAD method.
 *
 * @see wp_remote_request() For more information on the response array format.
 *
 * @since 2.7.0
 *
 * @param string $url Site URL to retrieve.
 * @param array $args Optional. Override the defaults.
 * @return WP_Error|array The response or WP_Error on failure.
 */
function wp_remote_head($url, $args = array()) {
	$objFetchSite = _wp_http_get_object();
	return $objFetchSite->head($url, $args);
}

/**
 * Retrieve only the headers from the raw response.
 *
 * @since 2.7.0
 *
 * @param array $response HTTP response.
 * @return array The headers of the response. Empty array if incorrect parameter given.
 */
function wp_remote_retrieve_headers(&$response) {
	if ( is_wp_error($response) || ! isset($response['headers']) || ! is_array($response['headers']))
		return array();

	return $response['headers'];
}

/**
 * Retrieve a single header by name from the raw response.
 *
 * @since 2.7.0
 *
 * @param array $response
 * @param string $header Header name to retrieve value from.
 * @return string The header value. Empty string on if incorrect parameter given, or if the header doesn't exist.
 */
function wp_remote_retrieve_header(&$response, $header) {
	if ( is_wp_error($response) || ! isset($response['headers']) || ! is_array($response['headers']))
		return '';

	if ( array_key_exists($header, $response['headers']) )
		return $response['headers'][$header];

	return '';
}

/**
 * Retrieve only the response code from the raw response.
 *
 * Will return an empty array if incorrect parameter value is given.
 *
 * @since 2.7.0
 *
 * @param array $response HTTP response.
 * @return string the response code. Empty string on incorrect parameter given.
 */
function wp_remote_retrieve_response_code(&$response) {
	if ( is_wp_error($response) || ! isset($response['response']) || ! is_array($response['response']))
		return '';

	return $response['response']['code'];
}

/**
 * Retrieve only the response message from the raw response.
 *
 * Will return an empty array if incorrect parameter value is given.
 *
 * @since 2.7.0
 *
 * @param array $response HTTP response.
 * @return string The response message. Empty string on incorrect parameter given.
 */
function wp_remote_retrieve_response_message(&$response) {
	if ( is_wp_error($response) || ! isset($response['response']) || ! is_array($response['response']))
		return '';

	return $response['response']['message'];
}

/**
 * Retrieve only the body from the raw response.
 *
 * @since 2.7.0
 *
 * @param array $response HTTP response.
 * @return string The body of the response. Empty string if no body or incorrect parameter given.
 */
function wp_remote_retrieve_body(&$response) {
	if ( is_wp_error($response) || ! isset($response['body']) )
		return '';

	return $response['body'];
}

/**
 * Determines if there is an HTTP Transport that can process this request.
 *
 * @since 3.2.0
 *
 * @param array  $capabilities Array of capabilities to test or a wp_remote_request() $args array.
 * @param string $url Optional. If given, will check if the URL requires SSL and adds that requirement to the capabilities array.
 *
 * @return bool
 */
function wp_http_supports( $capabilities = array(), $url = null ) {
	$objFetchSite = _wp_http_get_object();

	$capabilities = wp_parse_args( $capabilities );

	$count = count( $capabilities );

	// If we have a numeric $capabilities array, spoof a wp_remote_request() associative $args array
	if ( $count && count( array_filter( array_keys( $capabilities ), 'is_numeric' ) ) == $count ) {
		$capabilities = array_combine( array_values( $capabilities ), array_fill( 0, $count, true ) );
	}

	if ( $url && !isset( $capabilities['ssl'] ) ) {
		$scheme = parse_url( $url, PHP_URL_SCHEME );
		if ( 'https' == $scheme || 'ssl' == $scheme ) {
			$capabilities['ssl'] = true;
		}
	}

	return (bool) $objFetchSite->_get_first_available_transport( $capabilities );
}