$re = '/^((?:[A-Za-z0-9#\-_~!$&\'()*+,;=:]|[A-Za-z0-9#\-_~!$&\'()*+,;=:][A-Za-z0-9#\-_~!$&\'()*+,;=:\.]*[A-Za-z0-9#\-_~!$&\'()*+,;=:])@(?:[A-Za-z0-9]\.|[A-Za-z0-9][A-Za-z0-9#\-]{0,61}[A-Za-z0-9]\.)+(?:[A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9#\-]{0,61}[A-Za-z0-9]))\.?$/';
$str = ' ';
preg_match($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