$re = '/(\[.*?])\|(.*)\|(Description:.*)/';
$str = '[Testing.User]|Info:([Testing.Info]|Name:([System.String]|Matt)|Age:([System.Int32]|21))|Description:([System.String]|This is some description)
';
preg_match_all($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