$re = '/(?:(\"uuid\":\"(?<uuidValue>\w{8}-(?:(\w{4}-){3})\w{12}))\")/';
$str = '{"uuid":"ae7f5827-e29e-462f-b5f7-ace16cf5b18f","orderId":"ATLAS48315';
preg_match($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