$re = '/^[a-zA-Z]{2}[0-9]{2}\s?[a-zA-Z0-9]{4}\s?[0-9]{4}\s?[0-9]{3}([a-zA-Z0-9]\s?[a-zA-Z0-9]{0,4}\s?[a-zA-Z0-9]{0,4}\s?[a-zA-Z0-9]{0,4}\s?[a-zA-Z0-9]{0,3})?$/m';
$str = 'DE89 3704 0044 0532 0130 00
AT61 1904 3002 3457 3201
FR14 2004 1010 0505 0001 3
DE89370400440532013000
AT611904300234573201
FR1420041010050500013
DE89 370400440532013000
A T611904300234573201
FR1420 041010050500013';
preg_match_all($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