$re = '/<img src="([^"]*\.jpg)".*?class="threadlist_pic j_m_pic ".*?>/m';
$str = '<img src="http://tiebapic.baidu.com/forum/wh%3D200%2C90%3B/sign=ad58eff4b7ec08fa26551ba569de1154/ab92f5f50ad162d9a888295706dfa9ec8b13cdb7.jpg" attr="15621" data-original="http://tiebapic.baidu.com/forum/wh%3D200%2C90%3B/sign=ad58eff4b7ec08fa26551ba569de1154/ab92f5f50ad162d9a888295706dfa9ec8b13cdb7.jpg" bpic="http://tiebapic.baidu.com/forum/w%3D580%3B/sign=974a0cf05010b912bfc1f6f6f3c6fd03/ac4bd11373f0820200f4da745cfbfbedab641b12.jpg" class="threadlist_pic j_m_pic " style="display: inline;">
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php