what is wrong with this PHP Script
<p>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 :) </p>

<p>CODE: </p>

<pre><code>&lt;?php

  //require 'core.inc.php';



if(isset($_POST['username'])&amp;&amp; isset($_POST['password']) &amp;&amp; isset($_POST['passwordAgain'])&amp;&amp; isset($_POST['Firstname'])&amp;&amp; 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';
     }


}

?&gt;


&lt;form action="join.inc.php" method="POST"&gt;


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