$re = '/((http:\/\/sim\d{1,5}.agni.lindenlab.com:\d{4,5})(\/cap\/\w{8}-\w{4}-\w{4}-\w{4}-\w{12}))/';
$str = 'http://sim99991.agni.lindenlab.com:12046/cap/171ef743-106d-6a5f-119f-3fe098038d3d';
preg_match($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