proccess.php

<?php
error_reporting( E_ALL );
ini_set('display_errors',1);

register_shutdown_function( function(){
print_r( error_get_last() );
});
$username = isset($_POST['username']) ? $_POST['username'] : null;
$pass = isset( $_POST['password'] ) ? $_POST['password']  : null;
if( $username === null ){
          die("Required: Username");
} else if( $pass === null ){
          die("Required: Password");

} else {

    die( sprintf("Username: %s, Password: %s",$username, $pass ) );

}
?>