<form action="" method="POST">
Username : <input type="text" name="user"> Password :<input type="password" name="pass">
<input type="submit" value="Login">
<?php
if (isset($_POST['user']) && isset($_POST['pass']) && !empty($_POST['user']) && !empty($_POST['pass'])){
	$u=trim($_POST['user']);
	$p=trim($_POST['pass']);
	$k='mahmud';
	$l=123456;
	session_start();
		if($u==$k && $p==$l && $_SESSION['uname']=$k && $_SESSION['pas']=$l ) {
			echo '</br>welcome !!</br><input type="submit" value="Logout!!" name="out">';

		}else{
			echo '</br>Please input values correctly ';
		}


}



?>
<?php
if (isset($POST['out'])){
	session_start();
	session_destroy();

}

?>