如何通过php 获取页面中的指定内容类

<?php
/** grep class
*   Date:   2013-06-15
*   Author: fdipzone
*   Ver:    1.0
*
*   Func:
*
*   set:        设置内容
*   get:        返回指定的内容
*   replace:    返回替换后的内容
*   get_pattern 根据type返回pattern
*/
class Grep{ // class start
    private $_pattern = array(
                            'url' => '/<a.*?href="((http(s)?:\/\/).*?)".*?/si',
                            'email' => '/([\w\-\.]+@[\w\-\.]+(\.\w+))/',
                            'image' => '/<img.*?src=\"(http:\/\/.+\.(jpg|jpeg|gif|bmp|png))\">/i'
                        );
    private $_content = ''; // 源内容
    /* 設置搜尋的內容
    *  @param String $content
    */
    public function set($content=''){
        $this->_content = $content;
    }
    /* 获取指定内容
    *  @param String $type
    *  @param int    $unique 0:all 1:unique
    *  @return Array
    */
    public function get($type='', $unique=0){
        $type = strtolower($type);
        if($this->_content=='' || !in_array($type, array_keys($this->_pattern))){
            return array();
        }
        $pattern = $this->get_pattern($type); // 获取pattern
        preg_match_all($pattern, $this->_content, $matches);
        return isset($matches[1])? ( $unique==0? $matches[1] : array_unique($matches[1]) ) : array();
    }
    /* 获取替换后的内容
    *  @param String $type
    *  @param String $callback
    *  @return String
    */
    public function replace($type='', $callback=''){
        $type = strtolower($type);
        if($this->_content=='' || !in_array($type, array_keys($this->_pattern)) || $callback==''){
            return $this->_content;
        }
        $pattern = $this->get_pattern($type);
        return preg_replace_callback($pattern, $callback, $this->_content);
    }
    /* 根据type获取pattern
    *  @param String $type
    *  @return String
    */
    private function get_pattern($type){
        return $this->_pattern[$type];
    }
} // class end
?>

<?php
header('content-type:text/htm;charset=utf8');
require('Grep.class.php');
$content = file_get_contents('http://www.test.com/');
$obj = new Grep();
$obj->set($content);
$url = $obj->get('url', 0);
$email = $obj->get('email', 1);
$image = $obj->get('image', 1);
print_r($url);
print_r($email);
print_r($image);
$url_new = $obj->replace('url', 'replace_url');
echo $url_new;
function replace_url($matches){
    return isset($matches[1])? '[url]'.$matches[1].'[/url]' : '';
}
?>