$re = '/,(?=\s*\))/';
$str = 'item_id IN ( \'1\',\'2\',) AND nt_id IN ( \'er1\',\'er2\',) AND';
$subst = "";
$result = preg_replace($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