$re = '/\[img\](.*?)xyz_zyx_abc(.*?)\[\/img\]/';
$str = 'Test
[img]http://localhost/verz123/xyz_zyx_abc/70-300mm_IS_II_USM 331.jpg[/img]
test
';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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