Merubah fungsi ereg menjadi preg_match

Assalamualaikum,.. bukannya hanya ubah jadi begini saja :
if (preg_match("koneksi.php", $PHP_SELF))
 
// https://www.php.net/manual/en/migration53.deprecated.php

Assalamualaikum,.. 
sy sdh coba menggunakan  : if (preg_match("koneksi.php", $PHP_SELF))
muncul pesan kesalahan : Warning: preg_match(): Delimiter must not be alphanumeric or backslash in C:\xampp\htdocs\pmb_online\config.php on line 2
 
Notice: Undefined variable: PHP_SELF in C:\xampp\htdocs\pmb_online\koneksi.php on line 5
 
isi file konesi.php :
<?php
include "parser-php-version.php";
if (preg_match("koneksi.php", $PHP_SELF))
{
header("location:./index.php");
die;
}
 
function opendb()
{
global $dbhost, $dbuser, $dbpassword, $dbname, $dbconnection;
$dbconnection=mysql_connect($dbhost,$dbuser,$dbpassword)
or die ("Gagal Membuka Database");
$dbselect=mysql_select_db($dbname);
}
 
function closedb()
{
global $dbconnection;
mysql_close($dbconnection);
}
 
function querydb($query)
{
$result=mysql_query($query) or die ("Gagal Melakukan Query = $query");
return $result;
}
?>
 
dan config.php :
<?php
if (preg_match("config.php", $PHP_SELF))
{
header("location:./index.php");
die;
}
 
$dbhost="localhost";
$dbname="pmb_online";
$dbuser="root";
$dbpassword="";
?>
mohon bantuannya. terima kasih sebelumnya.