$re = '/script src=["\']?(\w+\.js)/';
$str = 'var a = \'<script class="anyClass" src="anyFile.js" id="anyID">\';
var b = \'<script class="anyClass" src="anyFile.js">\';
var c = \'<script src="anyFile.js" id="anyID">\';
var d = \'<script src="anyFile.js">\';
var e = "<script class=\'anyClass\' src=\'anyFile.js\' id=\'anyID\'>";
var f = "<script class=\'anyClass\' src=\'anyFile.js\'>";
var g = "<script src=\'anyFile.js\' id=\'anyID\'>";
var h = "<script src=\'anyFile.js\'>";
var i= "<script class=anyClass src=anyFile.js id=anyID>";
var j= "<script class=anyClass src=anyFile.js>";
var k= "<script src=anyFile.js id=anyID>";
var l= "<script src=anyFile.js>";';
preg_match_all($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