$re = '/^((\+?\d{1,4})?[-.\s]?\(?(\d{1,3})?\)?[-.\s]?(\d{1,4})[-.\s]?(\d{1,4})[-.\s]?(\d{1,9}))/m';
$str = '+49 172 7470791
+49 621 60-6641516
+49 621 60-41516
8-1-6641516
+7(927)296-96-08
61 41516
6641516
41516
';
$subst = "$2$3$4$5$6";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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