$re = '/NL\s?\d{2}\s?[A-Z]{4}0\s?\d{9}$
/m';
$str = 'IBAN NL 91ABNA0417164300
IBAN NL91ABNA0417164300
Iban: NL 69 ABNA 401022366';
preg_match_all($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