core class and global variables...
Well I've heard it many many times how global variables are bad and one should avoid it as much as possible. While I was browsing into Vbulletin and MyBB's core class(class Vbulletin/class MyBB), however, I found they were instantiating an object of the same name and passing it to function files as global $Vbulletin/global $MyBB frequently. The global object contains properties like cookies, session, currentuser and so on. If an object is declared as global, it is essentially a huge collection of global variables! Why would Vbulletin and MyBB do this? Or is the security issue for Global variables over-exaggerated by advanced programmers? I'm so confused now...
Also I've heard that dependency injection is a possible way to avoid using globals, but I have no idea how to use it. Anyone familiar with dependency injection here, and know how to replace globals by dependency injection? Just curious
Last edited by Lord Yggdrasill; 04-14-2012 at 08:16 AM.
High Energy Magic Dept.
As I understand it, DI just means that you inject and objects upon with the subject class depends via a method (which can include the constructor).
Note that you can use either instantiation technique as appropriate to your needs/preferences, e.g. the following would work just as well:
public function __construct(Dependency1 $dependency1)
$this->dependency1 = $dependency1;
public setDependency2(Dependency2 $dependency2)
$this->depenedency2 = $dependency2;
$d1 = new Dependency1();
$foo = new Foo($d1);
There are arguments for and against injecting the dependencies via the constructor or a setter method. I generally start with the constructor and move it to a setter if it seems better that way.
$foo = new Foo(new Dependency1());
$d2 = new Dependency2();
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