关于 php 通过 curl 的伪异步方式抓取数据，下面这种 curl 方式和普通的 curl 同步请求有什么区别？

下面是网上找到的一个类，是说可以实现 php 异步抓取数据，但是 php 一直是同步的，打印出的结果也是同步的，但是通过下面 rolling_curl 的方法，的确可以节省一定的时间，但是既然都是同步的 ，为什么会节约时间呢？ 希望各位大神能给出一些指导。 /**

• cURL 批量处理 工具类
• @since Version 1.0
• @author Justmepzy [email protected]
• @link http://t.qq.com/JustPzy */

	/** 

单一的请求对象 /
class Curl_request {
public $url = '';
public $method = 'GET';
public $post_data = null;
public $headers = null;
public $options = null;
/ *
* @param string $url * @param string $method * @param string $post_data * @param string $headers * @param array $options * @return void /
public function __construct($url, $method = 'GET', $post_data = null, $headers = null, $options = null) {
$this->url = $url;
$this->method = strtoupper( $method );
$this->post_data = $post_data;
$this->headers = $headers;
$this->options = $options;
}
/* * @return void /
public function __destruct() {
unset ( $this->url, $this->method, $this->post_data, $this->headers, $this->options );
}
}
/*

• 包含请求列队处理 /
  class Curl {
  /*

  • 请求 url 个数

  • @var int /
    private $size = 1; /*

  • 等待所有 cURL 批处理中的活动连接等待响应时间

  • @var int /
    private $timeout = 5; /*

  • 完成请求回调函数

  • @var string /
    private $callback = null;
    /*

  • cRUL 配置

  • @var array /
    private $options = array (CURLOPT_SSL_VERIFYPEER => 0,CURLOPT_RETURNTRANSFER => 1,CURLOPT_CONNECTTIMEOUT => 30 );
    /*

  • 请求头

  • @var array /
    private $headers = array ();
    /*

  • 请求列队

  • @var array /
    private $requests = array ();
    /*

  • 请求列队索引

  • @var array /
    private $request_map = array ();
    /*

  • 错误

  • @var array /
    private $errors = array ();
    /*

  • @access public

  • @param string $callback 回调函数

  • 该函数有 4 个参数($response,$info,$error,$request)

  • $response url 返回的 body

  • $info cURL 连接资源句柄的信息

  • $error 错误

  • $request 请求对象 /
    public function __construct($callback = null) {
    $this->callback = $callback;
    }
    /*

  • 添加一个请求对象到列队

  • @access public

  • @param object $request

  • @return boolean /
    public function add($request) { $this->requests [] = $request;
    return TRUE;
    }
    /*

  • 创建一个请求对象并添加到列队

  • @access public

  • @param string $url

  • @param string $method

  • @param string $post_data

  • @param string $headers

  • @param array $options

  • @return boolean /
    public function request($url, $method = 'GET', $post_data = null, $headers = null, $options = null) {
    $this->requests [] = new Curl_request ( $url, $method, $post_data, $headers, $options );
    return TRUE;
    }
    /*

  • 创建 GET 请求对象

  • @access public

  • @param string $url

  • @param string $headers

  • @param array $options

  • @return boolean /
    public function get($url, $headers = null, $options = null) {
    return $this->request ( $url, "GET", null, $headers, $options );
    }
    /*

  • 创建一个 POST 请求对象

  • @access public

  • @param string $url

  • @param string $post_data

  • @param string $headers

  • @param array $options

  • @return boolean /
    public function post($url, $post_data = null, $headers = null, $options = null) {
    return $this->request ( $url, "POST", $post_data, $headers, $options );
    }
    /*

  • 执行 cURL

  • @access public

  • @param int $size 最大连接数

  • @return Ambigous <boolean, mixed>|boolean /
    public function execute($size = null) {
    if (sizeof ( $this->requests ) == 1) {
    return $this->single_curl ();
    } else { return $this->rolling_curl ( $size ); }
    }
    /*

  • 单个 url 请求

  • @access private

  • @return mixed|boolean */
    private function single_curl() { $ch = curl_init (); $request = array_shift ( $this->requests ); $options = $this->get_options ( $request ); curl_setopt_array ( $ch, $options ); $output = curl_exec ( $ch ); $info = curl_getinfo ( $ch );

    // it's not neccesary to set a callback for one-off requests if ($this->callback) { $callback = $this->callback; if (is_callable ( $this->callback )) { call_user_func ( $callback, $output, $info, $request ); } } else return $output; return true; }
    /**

  • 多个 url 请求

  • @access private

  • @param int $size 最大连接数

  • @return boolean */
    private function rolling_curl($size = null) {
    if ($size)
    $this->size = $size;
    else
    $this->size = count($this->requests);
    if (sizeof ( $this->requests ) < $this->size)
    $this->size = sizeof ( $this->requests );
    if ($this->size < 2)
    $this->set_error ( 'size must be greater than 1' );
    $master = curl_multi_init ();
    //添加 cURL 连接资源句柄到 map 索引
    for($i = 0; $i < $this->size; $i ++) {
    $ch = curl_init (); $options = $this->get_options ( $this->requests [$i] ); curl_setopt_array ( $ch, $options );
    curl_multi_add_handle ( $master, $ch );

     $key = ( string ) $ch;  
     $this->request_map [$key] = $i;  
    

    }

    $active = $done = null;
    do {
    while ( ($execrun = curl_multi_exec ( $master, $active )) == CURLM_CALL_MULTI_PERFORM )
    ;
    if ($execrun != CURLM_OK)
    break;
    //有一个请求完成则回调
    while ( $done = curl_multi_info_read ( $master ) ) {
    //$done 完成的请求句柄
    $info = curl_getinfo ( $done ['handle'] );//
    $output = curl_multi_getcontent ( $done ['handle'] );//
    $error = curl_error ( $done ['handle'] );//

         $this->set_error ( $error );  
    
         //调用回调函数,如果存在的话  
         $callback = $this->callback;  
         if (is_callable ( $callback )) {  
             $key = ( string ) $done ['handle'];  
             $request = $this->requests [$this->request_map [$key]];  
             unset ( $this->request_map [$key] );
             call_user_func ( $callback, $output, $info, $error, $request );
         }  
         curl_close ( $done ['handle'] );  
         //从列队中移除已经完成的 request  
         curl_multi_remove_handle ( $master, $done ['handle'] );  
     }  
     //等待所有 cURL 批处理中的活动连接  
     if ($active)  
         curl_multi_select ( $master, $this->timeout );  
    

    } while ( $active );
    //完成关闭
    curl_multi_close ( $master );
    return true;
    }
    /**

  • 获取没得请求对象的 cURL 配置

  • @access private

  • @param object $request

  • @return array */
    private function get_options($request) {
    $options = $this->__get ( 'options' );
    if (ini_get ( 'safe_mode' ) == 'Off' || ! ini_get ( 'safe_mode' )) {
    $options [CURLOPT_FOLLOWLOCATION] = 1;
    $options [CURLOPT_MAXREDIRS] = 5;
    }
    //$headers = $this->__get ( 'headers' );
    $headers = $request->headers;
    if ($request->options) {
    $options = $request->options + $options;
    }

    $options [CURLOPT_URL] = $request->url;

    if ($request->post_data && strtolower($request->method) == 'post' ) {
    $options [CURLOPT_POST] = 1;
    $options [CURLOPT_POSTFIELDS] = $request->post_data;
    }

    if ($headers) {
    $options [CURLOPT_HEADER] = 0;
    $options [CURLOPT_HTTPHEADER] = $headers;
    }

    return $options;
    }
    /**

  • 设置错误信息

  • @access public

  • @param string $msg /
    public function set_error($msg) {
    if (! empty ( $msg ))
    $this->errors [] = $msg;
    }
    /*

  • 获取错误信息

  • @access public

  • @param string $open

  • @param string $close

  • @return string /
    public function display_errors($open = '

    ', $close = '

    ') {
    $str = '';
    foreach ( $this->errors as $val ) {
    $str .= $open . $val . $close;
    }
    return $str;
    }
    /*

  • @access public

  • @param string $name

  • @param string $value

  • @return boolean /
    public function __set($name, $value) {
    if ($name == 'options' || $name == 'headers') {
    $this->{$name} = $value + $this->{$name};
    } else {
    $this->{$name} = $value;
    }
    return TRUE;
    }
    /*

  • @param string $name

  • @return mixed

  • @access public /
    public function __get($name) {
    return (isset ( $this->{$name} )) ? $this->{$name} : null;
    }
    /*

  • @return void

  • @access public /
    public function __destruct() {
    unset ( $this->size, $this->timeout, $this->callback, $this->options, $this->headers, $this->requests, $this->request_map, $this->errors );
    }
    }
    // END Curl Class
    / End of file curl.class.php */