PHP Problem

<?php
function checkAccount($username, $password){
    include("INC/dbconnect.inc");/*"INC/dbconnect.inc" is <?php $pdo = new PDO("mysql:host=localhost;dbname=socialnetwork","user","123"); ?>*/
    $select = $pdo->prepare("SELECT id,password FROM users WHERE user_username = :username");
    $select->execute(array(':username'=>$username));
    $q_rows = $select->fetchAll();
    if($q_rows[0][0]/*the ID of the user, it should always be greater than 1, if not then the username does not exist*/ > 0 && $q_rows[0][0] != null){
        if($q_rows[0][1]/*the password of the user*/ == $password)
            return "true";
        else
            return "false";
    }
    else
        return "false";
    $pdo=null;
}

if(isset($_POST["submit"])){
    $userData = array();
    $userData[0] = $_POST['username'];
    $userData[1] = hash("sha512", $_POST['password']);

    if(checkAccount($userData[0], $userData[1])){
        echo "<div class=\"formconfirm\">
            <table border=\"0\">
            <tr>
            <td>
            <img src=\"http://cdn1.iconfinder.com/data/icons/onebit/PNG/onebit_34.png\" />
            </td>
            <td>
            You have successfully logged in! Redirecting...
            </td>
            </tr>
            </table>
            </div>";
    }
    else{
        echo "<div class=\"formerror\">
            <table border=\"0\">
            <tr>
            <td>
            <img src=\"http://cdn1.iconfinder.com/data/icons/icojoy/noshadow/standart/gif/24x24/001_30.gif\" />
            </td>
            <td>
            Incorrect Username or Password.
            </td>
            </tr>
            </table>
            </div>";
    }
}

?>
<h2>Login</h2>
<p>Login now to start seeing Community Service updates!</p>
<form method="post" action="">
<table border="0">
    <tr>
    <td align="right">Username</td>
    <td>
    <?php
    if(isset($_POST['submit']))
        echo "<input class=\"inputGood\" type=\"text\" name=\"username\" value=\"$userData[0]\"/>";
    else
        echo "<input class=\"inputGood\" type=\"text\" name=\"username\"/>";
    ?>
    </td>
    </tr>
<tr>
</tr>
    <tr>
    <td align="right">Password</td>
    <td><input class="inputGood" type="password" name="password" /></td>
</tr>
<tr>
<td colspan="1" align="center"><input type="submit" name="submit" value="    Login    " /></td>
</tr>
</table>
</form>