$re = '/\b\d{2} \d{3} \d{3} \d{3}\b|\b\d{11}\b|\b\d{2} \d{6} \d{3}\b|\b\d{8} \d{3}\b|\b\d{2} \d{4} \d{5}\b|\b\d{2} \d{9}\b/m';
$str = '12 345 678 901';
preg_match_all($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