使用fetchAll（）从PDO对象中进行选择

For some reason the following code always returns true, no matter what the parameter is and what is actually inside of the SQL row. It also throws an error "Notice: Undefined offset: 0 in C:\wamp\www\Social Networking\INC\login.inc on line 7" but I do not see what is wrong:

<?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;
} ?>

Can someone please tell me what is wrong? I have commented inside of the code the problems I am experiencing, and I have tried normal $select->fetch() instead of $select->fetchAll() to no avail. I have read up on PDO before posting this (http://php.net/manual/en/pdostatement.fetchall.php). Here is the rest of my file http://pastebin.com/YCkrRivs, thanks.

If the database returns no rows, then there will be no entry $q_rows[0]. Hence, undefined offset 0 as you are trying to retrieve a row in array that doesn't exist. Your 'ID' not > 0 for non-existent user is not a correct summary.

Sample return looks like this (if you print_r()'d it)

User present:

$q_rows = Array (
  [0] => Array ( 
   [id] => 1,
   [password] => 'dno23n3io3'
  )
)

No user present:

$q_rows = Array (
)

You should do:

if(size($q_rows) > 0) {
   //Handle user present
} else {
   //Handle no user present
}

You don't need to use fetchAll, just use fetch:

$q_row = $select->fetch();

if ($q_row) {
  // do your logic ...
}

And you are returning strings "true"/"false", not the boolean, you should use true/false instead.

More simple, you could just do like below:

$q_row = $select->fetch();
return $q_row && $q_row[0] > 0 && $q_row[1] === $password;