$re = '/\<script\>[^<]*?(findthis).*?\<\/script\>/s';
$str = '<html>
<head>
<script>
var x = 1;
var y = \'findthis\'; // Should be matched
</script>
</head>
<body>
<script>
var a = 2;
</script>
<h1>Welcome!</h1>
<p>This findthis here should not be matched.</p>
<script>
var b = \'findthis too\'; // Should be matched, too.
</script>
<div>
<p>This findthis should not be matched neither.</p>
</div>
</body>
</html>';
preg_match_all($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