$re = '/([a-zA-Z\:]){4,100}([a-zA-Z0-9]{8}[:-]([a-zA-Z0-9]{4}[:-]){3}[a-zA-Z0-9]{12})/';
$str = 'urn:vcloud:user:2998042f-b91d-4c16-9de8-7feaf5e711a8
';
$subst = "";
$result = preg_replace($re, $subst, $str, 1);
echo "The result of the substitution is ".$result;
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