curl_dump.php

<?php
/** 
 * Plugin Name: (#81791) Dump cURL Request & Response 
 * Author:      Franz Josef Kaiser
 */
add_action( 'plugins_loaded', array( 'WPSE81791_cURL', 'init' ) );
class WPSE81791_cURL
{
    protected static $instance;

    public static $dump;

    public static function init()
    {
        null === self :: $instance AND self :: $instance = new self;
        return self :: $instance;
    }

    public function __construct()
    {
        add_action( 'http_api_curl', array( $this, 'dump_curl' ) );
        add_action( 'shutdown', array( $this, 'do_dump' ) );
    }

    /**
     * Debug the response in the middle.
     * Catches the cURL object during the request.
     * @param  cURL $handle
     * @return void
     */
    public function dump_curl( &$handle )
    {
        curl_setopt( $handle, CURLINFO_HEADER_OUT, 1 );
        curl_setopt( $handle, CURLOPT_HEADER, 0 );
        curl_setopt( $handle, CURLOPT_HEADERFUNCTION, array( $this, 'dump_curl_buffer_cb' ) );
        curl_setopt( $handle, CURLOPT_WRITEFUNCTION, array( $this, 'dump_curl_buffer_cb' ) );
        curl_exec( $handle );
        $this->add_dump(
             curl_getinfo( $handle, CURLINFO_HEADER_OUT )
            .$this->dump_curl_buffer_cb( null )
            .'<br />Curl Error Code: '.curl_errno( $handle )
            .'<br />Errors: '.curl_error( $handle )
        );
    }

    /**
     * Callback for cURL dump method
     * @param  object $curl
     * @param  null   $data
     * @return int
     */
    public function dump_curl_buffer_cb( $curl, $data = null )
    {
        static $buffer = '';
        if ( is_null( $curl ) )
        {
            $r = $buffer;
            $buffer = '';
            return $r;
        }
        $buffer .= $data;
        return strlen( $data );
    }

    /**
     * Adds data to the static data stack
     * @param  
     * @return void
     */
    public function add_dump( $data )
    {
        self :: $dump[] = $data;
    }

/**
     * Dumps the data stack for debug
     * @param  
     * @return void
     */
    public function do_dump()
    {
        ! empty( self :: $dump ) AND printf(
             '<pre>%s</pre>'
            ,var_export( implode( "<br />", self :: $dump ), true ) 
        );
    }
}