- var_dump: documentation ( source)
- preg_match: documentation ( source)
- filter_var: documentation ( source)
<?php
$str = 'November 1997';
$str2 = 'November 20, 2001';
$matches;
preg_match('/\d{4}/', $str,$matches);
var_dump(
(int) $str,
intval($str),
filter_var($str, FILTER_SANITIZE_NUMBER_INT),
$matches
);