Function Dependancy PHP - php

Question

So in php im trying to get a public variable in the database class that connects to a database when the class is created. Like so -
<?php
class database {
public $_link;
public function __construct (){
$this->_link = new PDO("mysql:host=localhost; dbname=swinkidc_student", "swinkidc_student", "");
}
}
and...
<?php
class user{
private $db;
public function __construct() {
$this->db = new database;
}
/**
* Returns the ID of a user.
* #param string $user
* #return mixed
*/
public function getUserID($user){
$query = $_link->prepare("SELECT `user_id` FROM `users` WHERE `username` = :user");
$query->bindParam(":user", $user);
$query->execute();
$result = $query->fetch(PDO::FETCH_ASSOC);
return $result['user_id'];
}
/**
* Checks if given user is active.
* #param string $user
* #return bool Returns true/false if user is active.
*/
public function isUserActive($user){
}
}
If I extened database in user I can obviously refer to _link if i make it private and it will work, however, I don't think that i should inherit just for getting something like that..
Whenever i try the about i get :
Fatal error: Call to a member function prepare() on a non-object in /home/swinkidc/public_html/studentreach/core/authentication/user.php on line 18
As said, if i try the inheritance way it will work, I just don't feel like thats a great way of doing something like this.
Any suggestions please?
Thanks!

Answer 1

link is actually a property of database and not a property of user. Therefore use:
$query = $this->db->_link->...

Answer 2

You are just missing the $this->db-> before:
$query = $this->db->_link->prepare("SELECT `user_id` FROM `users` WHERE `username` = :user");
Now, it should work; you're trying to access it directly. First access the Database-link holding object through the $this->db and only then access the property $_link.
If you need $_link as a variable because it's shorter, assign the object $this->db->_link to $_link:
$_link = $this->db->_link;
At the beginning of your getUserID function, then it'll work too.

Answer 3

Try, in the User class, something as:
<?php
class user{
private $db;
public function __construct() {
$this->db = new database;
}
/**
* Returns the ID of a user.
* #param string $user
* #return mixed
*/
public function getUserID($user){
$query = $this->db->_link->prepare("SELECT `user_id` FROM `users` WHERE `username` = :user");
$query->bindParam(":user", $user);
$query->execute();
$result = $query->fetch(PDO::FETCH_ASSOC);
return $result['user_id'];
}
/**
* Checks if given user is active.
* #param string $user
* #return bool Returns true/false if user is active.
*/
public function isUserActive($user){
}
}
This can works as _link is not a attribute of User, but of database, and, if you extend the class database, it's acessible from the methods in link (at least in Java, i not know if the same way works for PHP), but not if you just instantiate it. It's just basic OOP.
Good luck.

Answer 4

Better to invert dependencies and wrap $db.
class database {
private $_link;
public function __construct(\PDO $pdo) {
$this->_link = $pdo;
}
public function getLink() {
return $this->_link;
}
//other useful stuff
}
class user {
private $_db;
public function __construct(\database $db) {
$this->_db = $db;
}
public function getDB() {
return $this->_db;
}
/**
* Returns the ID of a user.
* #param string $user
* #return mixed
*/
public function getUserID($user) {
$query = $this->getDB()->getLink()->prepare("SELECT `user_id` FROM `users` WHERE `username` = :user");
$query->bindParam(":user", $user);
$query->execute();
$result = $query->fetch(PDO::FETCH_ASSOC);
return $result['user_id'];
}
/**
* Checks if given user is active.
* #param string $user
* #return bool Returns true/false if user is active.
*/
public function isUserActive($user) {
}
}
Usage
$user = new \user(new \database(new \PDO("mysql:host=localhost; dbname=swinkidc_student", "swinkidc_student", "")));
Now you can configure your db connection outside of the class.