PHP call to static function fails - php

Question

All,
I'm getting an error with the code below. Here is the error message I get:
Notice: Undefined variable: userDAO in C:\wamp\www\Projetv0.2\Model_User.php on line 15
and then
Fatal error: Call to a member function checkRecordExists() on a non-object in C:\wamp\www\Projetv0.2\Model_User.php on line 15
The relevant code is below. What I try to do with the code is have a unique class (DAO_DBrecord) to access several tables in a db. In the case below, I want to access my users table. To do that I have created a specific static function createUserDAO inside the DAO_DBrecord class that calls the constructor with the right table name, users. However, it doesn't work, and I can't figure why.
Model_User.php:
<?php
require_once('Class_DB.php');
require_once('DAO_DBrecord.php');
class Model_user{ // Represents a connection to the users table in the DB
private $db;
private $userDAO;
function __construct($db){
$this->db=$db;
$userDAO=DAO_DBrecord::createUserDAO($this->db);// static function - calls constructor w/ 'user' table name parameter
$this->userDAO=$userDAO;
}
function userInfoExists($userInfo, $colName){
return $userDAO->checkRecordExists($userInfo, $colName);
}
//Other stuff
}
?>
DAO_DBrecord.php:
<?php
require_once('Class_DB.php');
class DAO_DBrecord {
private $db;
private $table;
private function __construct($db,$table){
$this->db=$db;
$this->table=$table;
}
public static function createUserDAO($db) {
return new DAO_DBrecord($db, 'users');
}
//Other stuff
}
?>
Thank you all for your help!
JDelage

Answer 1

That's not a problem with the static function. The problem is that PHP doesn't have an implicit $this. When you're referring to the member variable within the class (as you are in userInfoExists), you have to say $this->userDAO rather than just $userDAO.
Of course, all this assumes that the DAO_DBrecord class has or inherits a checkRecordExists function. If it doesn't, you're going to have other problems.