<?php
$uyeler= array(
array("Deneme","123"),
array("Uye2","Sifresi"),
array("Uye3","Uye3")
);

$kadi= $_POST["kadi"];
$sifre= $_POST["sifre"];


if(in_array(array($kadi,$sifre),$uyeler)){
echo "giriş yaıldı";
}else{
echo "üye yok";
}

?>