这个PHP脚本有什么问题

Question

Hey all i am working on a simple registration form and i have done a simple test on it. basically i said if the username filed is empty and we click submit it will echo out 'all filed's are required' else Ok. My code looks fine or else i am going insane can some one have a look for me thank you :)

CODE:

<?php

  //require 'core.inc.php';



if(isset($_POST['username'])&& isset($_POST['password']) && isset($_POST['passwordAgain'])&& isset($_POST['Firstname'])&& isset($_POST['Lastname'])){

    $username = $_POST['username'];
    $password = $_POST['password'];
    $password_again = $_POST['passwordAgain'];
    $Firstname = $_POST['Firstname'];
    $Lastname = $_POST['Lastname'];

    if(!empty($username)){

        echo 'OK.';

    }else{

   echo 'fill in all details thank you';
     }


}

?>


<form action="join.inc.php" method="POST">


    Username: <input type="text" name="username" /><br />
    Password: <input type="password" type="password" /><br />
    Password Again: <input type="password" type="passwordAgain" /><br />
    FirstName: <input type="text" name ="Firstname"/><br />
    LastName: <input type="text" name ="Lastname" /><br />
    <input type="submit" value="SUBMIT" />
</form>

Answer 1

Rectify this:

 Password: <input type="password" name="password" /><br />
 Password Again: <input type="password" name="passwordAgain" /><br />