OOP global variables

[Manixat]

Hello freaks,

 

I am having quite a difficult time working out how to use an instance of a certain class in all instances of all objects.

 

Example:

this is my main file ( index etc. ),

 

 

 

<?php

$a = new User();

$b = new HeaderBuilder($_SESSION['userid']);

?>
 

 

 

HeaderBuilder:

 

 

<?php
 
class HeaderBuilder{
 
    function __construct($id){
    echo $a->getUserById($id);
    }
 
}

 

Now my question is how do I use $a in HeaderBuilder's __construct without creating a new instance ?

[ignace]

Just pass the instance to the HeaderBuilder's constructor.

class HeaderBuilder {

  private $user;


  public function __construct(User $user) {

    $this->user = $user;

  }

}

[Manixat]

This is logical but I just want it to be a single variable. Doing that to all my methods where I need user() is going to be a pain in the you know what. I tried with $_GLOBALS and it worked but it is just so long and annoying to type every time. Why can't I just simply assign a global variable in the main file O.o

[Hall of Famer]

Well good OOP design requires no global variable or at least minimum usage of globals. Technically you can achieve the same functionality as global variables with Singleton/Registry pattern, but these are often considered anti-patterns.

[Manixat]

I have heard that using global variables in OOP is bad, but I just don't see the logic in creating a hundred instances of a class in a single page build when you can ( or I hope I can ) use a global one :/

[ignace]

When you pass a class to another class, you pass the reference to the original instance you don't create a new object.

$u = new User('ignace');


$a = new Foo($u);

$b = new Foo($u);

$c = new Foo($u);

$d = new Foo($u);


$u->setName('Manixat');

$c->printUserName(); // Manixat

$d->printUserName(); // Manixat

This is different from your normal procedural thinking. No matter how you turn it though if your class has a dependency on another class you'll still have to type it. Show us an example of what you mean by that you have to pass/create an instance in other classes.

[Manixat]

What I was actually looking for was indeed singleton, I just haven't had read about it in depth and understood it well. Now that I do, it's exactly what I needed, thank you for your replies!

[trq]

Nooo..... singletons are almost always not needed and they make it very easy to make your code tightly coupled.

 

Post what you have.

[SurvivorZ]

I am positive that what you want is a Factory instead of the Singleton.

 

But really, what you want to research is called Constructor-based Dependency Injection.