$re = '/(?:src=\")(?P<URL>.*)\"/';
$str = '![enter image description here][1] [1]: <img src="http://www.codefixup.com/wp-content/uploads/2016/09/pattern-matching-in-php.png" />';
preg_match($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