Can't get my php code to post into my mysql database

Hi there,

I am creating a simple form to post some information into a database. I can't work out what I am doing wrong. I keep getting the 'Sorry, your registration failed. Please go back and try again.'. First time I tried it, it worked. I can't work out why it hasn't worked since.

The first stage works: $checkusername = mysql_query("SELECT * FROM users WHERE username = '".$username."'"); as if I type in a matching name then I get the ' Sorry, that username is taken. Please go back and try again.' message.

I just can't get the code to insert into my db and then give me the success message!

I know that this code is not very safe at this stage and I need to update my mysql_query statements, I just want my code to work so I can get onto these bigger problems.

I have been looking at this for a day I can't work out why, some help would be much appreciated, none of the courses on treehouse really cover this area.

Thank you very much in advance.

Here's the code:

<?php include "connection.php"; ?>

<?php if(!empty($_POST['username']) && !empty($_POST['password'])) { $username = mysql_real_escape_string($_POST['username']); $password = md5(mysql_real_escape_string($_POST['password'])); $email = mysql_real_escape_string($_POST['email']);

 $checkusername = mysql_query("SELECT * FROM users WHERE username = '".$username."'");

 if(mysql_num_rows($checkusername) == 1)
 {
    echo "<h1>Error</h1>";
    echo "<p>Sorry, that username is taken. Please go back and try again.</p>";
 }
 else
 {
     $registerquery = mysql_query("INSERT INTO users (username, password, email) VALUES('".$username."', '".$password."', '".$email."')");

     mysql_query($registerquery);

    if($registerquery)
    {
        echo "<h1>Success</h1>";
        echo "<p>Your account was successfully created. Please <a href=\"login.php\">click here to login</a>.</p>";
    }
    else
    {
        echo "<h1>Error</h1>";
        echo "<p>Sorry, your registration failed. Please go back and try again.</p>";
    }       
 }

} else { ?>

<h1>Register</h1>

<p>Please enter your details below to register.</p>

<form method="post" action="register.php" name="registerform" id="registerform">
<fieldset>
    <label for="username">Username:</label><input type="text" name="username" id="username" /><br />
    <label for="password">Password:</label><input type="password" name="password" id="password" /><br />
    <label for="email">Email Address:</label><input type="text" name="email" id="email" /><br />
    <input type="submit" name="register" id="register" value="Register" />
</fieldset>
</form>

<?php

} ?>