<?php
define('HOST','localhost');
define('USER','');
define('PASS','');
define('DB','user');

$con = mysqli_connect(HOST,USER,PASS,DB);

$username = $_POST['uname'];
$password = $_POST['pass'];

$sql = "select * from mytable where uname='$username' and pass='$password'";

$res = mysqli_query($con,$sql);

$check = mysqli_fetch_array($res);

if(isset($check)){
echo 'success';
}else{
echo 'failure';
}

mysqli_close($con);
?>