$re = '/^(?:(?:\+|00)(\d+)[ ]?|(?:\+\+|0))(\d{2})[ ]?(\d{3})[ ]?(\d{2})[ ]?(\d{2})$/m';
$str = '+41 51 271 21 44
++51 271 21 44
++51 271 21 44
051 271 21 44
0512712144
0041512712144
051 271 21 44
051 271 21a44
0041 51 271 21 44
';
preg_match_all($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