$re = '/src="(\S*)"/m';
$str = '<p>< img class="wscnph" style="display: block; margin-left: auto; margin-right: auto;" src="http://mnc-skin.oss-cn-shanghai.aliyuncs.com/production%2Farticle%2F319ed92bf0e5431f84985bd736ea03b7.jpg?OSSAccessKeyId=LTAIQ8Lif1HHVkXd&Expires=9223372038484041640&Signature=ilG%2BdTUMdQSEzHGaPZzoH7XpvZA%3D" /></p >';
preg_match_all($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