Methods as objects - How / when

Question

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PHP method chaining?

In a lot of APIs I've worked with, I've seen this sort of thing:

$object->method()->anotherMethod();

From the tutorials on OOP that I've read, this is how classes are written,

<?php
class myClass {
    public method() {
       // do something
    }
}
?>

When should this be used, and how can it be done? Apologies, but I am new to OOP.

the method isn't an object, it returns an object (usually the same object as the first one) and the second method is called on that object — Esailija, May 27 '12 at 12:51
Is it possible to make it return another object? eg In the APIs I've used, the methods in $object are different to those in $object->method(). EDIT: You could use 'return new class();'? — Jared, May 27 '12 at 12:56
also https://secure.wikimedia.org/wikipedia/en/wiki/Law_of_Demeter — Gordon, May 27 '12 at 13:08

score 4 · Accepted Answer · answered May 27 '12 at 12:51

If your method returns $this, you will be able to use the above style ($object->method()->anotherMethod()). This can be done only in cases where your method is not expected to return something else, e.g. a method named like getSomething() is expected to return Something, but if you have a method that has no relevant value to return, you can just return $this, allowing method call chains.

score 3 · Answer 2 · answered May 27 '12 at 12:52

This is called Method Call Chaining. There are no hard and fast rules about when you should use it, but the general rule I use is that method chaining makes sense when there are a series of object methods that are frequently called one after the other, such as initialization functions.

Methods as objects - How / when

2 Answers2