How to make this live validation work with my sql PDO - php

Question

my intention is to make a live validation , which i found a side that tutorial but they are using old sql , i wanted to use my sql PDO , but i cant make it work , even my database having the same name , it still say ok.
how do i make it work , before you check my code , please look and download the link to check it out, thank.
download from here:
Please Check This Link
my code(i changed some to PDO but still wont work)
dbConnector.php
<?php
class DbConnector {
var $link;
function DbConnector(){
try{
$this->link = new PDO('mysql:host=127.0.0.1;dbname=system', 'root', '123456');
$this->link->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$this->link->setAttribute(PDO::ATTR_EMULATE_PREPARES,false);
}catch(PDOException $e){
die("this is not connected");
}
}
//*** Function: query, Purpose: Execute a database query ***
function query($query) {
try{
$this->link->prepare($query);
}catch(PDOException $e){
die("fail to prepare");
}
return $this->link;
}
}
?>
check.php
<?php
include("dbConnector.php");
$connector = new DbConnector();
$username = trim(strtolower($_POST['username']));
$query = "SELECT air_users FROM USER_NAME WHERE username = ? LIMIT 1";
$result = $connector->query($query);
$result->execute(array($username));
$num = $result->rowCount();
$num = $result->fetch();
echo $num;
// mysql_close();
?>
i dont have any error , but still it wont work. thank for helping out.

Answer 1

You need to return the returned value of $this->link->prepare($query); not the $this->link itself. To make it work, rewrite your query this way:
function query($query) {
return $this->link->prepare($query);
}

Answer 2

I don't think that the $username variable is been interpreted on the string, as you have it.
"SELECT users FROM USER_NAME WHERE username = :username' LIMIT 1";
...
execute(array(':username' => $username));
and on the query method call prepeare like:
$this->link->prepare($query, array(PDO::ATTR_CURSOR => PDO::CURSOR_FWDONLY));
or
"SELECT users FROM USER_NAME WHERE username = ? LIMIT 1";
...
execute(array($username));
And the prepare method should be call like you have it on your example:
$this->link->prepare($query);
And on the query method you return the $query or the string. You should return the instance or execute in the query method.
function query($query) {
try{
$this->link->prepare($query);
}catch(PDOException $e){
die("fail to prepare");
}
return $this->link;
}
See