$re = '/&room:([a-f\d-]+)/i';
$str = 'stringVar=email:name@company.com&room:b83edd0d-fec5-4ec0-8055-60bc0d8eb4b6;
stringVar=email:name@company.com&room:b83edd0d-fec5-4ec0-8055-60bc0d8eb4b6&host=HOSTNAME;
stringVar=email:name@company.com&location=SomeCity&room:b83edd0d-fec5-4ec0-8055-60bc0d8eb4b6;';
preg_match_all($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