signup.php

<?php
    require_once 'header.php';

    echo<<<_END
    <script>
        function checkUser(user){
            if(user.value == ''){
                $('#used').html('&nbsp;')
                return;
            }
            $.post(
                'checkuser.php',
                { user: user.value},
                function(data){
                    $('#used').html(data)
                }
            )
        }
    </script>
    _END;

    $error = $user = $pass = "";
    if(!empty($_SESSION['user'])) destroySession();

    if(!empty($_POST['user'])){
        $user = sanitizeString($_POST['user']);
        $pass = sanitizeString($_POST['pass']);

        if($user == "" || $pass == ""){
            $error = 'Not all fields were entered<br><br>';
        }
        else{
            $result = queryMysql("SELECT * FROM members WHERE user='$user'");

            if($result->num_rows){
                $error = 'That username already exists<br><br>';
            }
            else{
                queryMysql("INSERT INTO members VALUES('$user','$pass')");
                die("<h4>account created</h4>Please log in.</div></body></html>");
            }
        }
    }
    echo <<<_END
            <form method='post' action='signup.php'>$error
            <div data-role='fieldcontain'>
                <label></label>
                Please enter your details to sign up
            </div>
            <div data-role='fieldcontain'>
                <label>Username</label>
                <input type='text' maxlength='16' name='user' value='$user'
                    onBlur='checkUser(this)'>
                <label></label><div id='used'>&nbsp;</div>
            </div>
            <div data-role='fieldcontain'>
                <label>Password</label>
                <input type='text' maxlength='16' name='pass' value='$pass'>
            </div>
            <div data-role='fieldcontain'>
                <label></label>
                <input data-transition='slide' type='submit' value='Sign Up'>
            </div>
        </div>
        </body>
    </html>
    _END;
?>