$re = '/(.)(\d\d\d\d)/m';
$str = 'La.chambre.des.officiers.2001
The.2nd.2020
The.Song.of.Names.2020';
$subst = "$1($2)";
$result = preg_replace($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