PHP and static class methods

Question

I am looking for a better understanding of how static methods work in php. I have been reading the article on the php manual site about static keyword in releation to methods, and class objects and I am curious about something.

Lets say I have this class:

class Something{
    protected static $_something = null;

    public function __construct($options = null){
        if(self::$_something === null && $options != null){ 
            self::$_something = $options 
        }
    }

    public function get_something(){ return self::$_something }
}

So you instantiate this on index.php, so you do something like:

$class_instantiation = new Something(array('test' => 'example'));

Great, at this point $_something contains an array of key=>value, on this same page we can do:

var_dump($class_instantiation->get_something()); // var dumps the array we passed in.

BUT

If we now create sample.php and do:

$class_instantiation = new Something();
var_dump($class_instantiation->get_something());

We get null back (I assume you went to index.php, instantiated the class and passed in the array, saw the var_dump THEN navigated to sample.php. It is understandable how this would return null if you only went to sample.php without first going to index.php.)

I assumed that static methods are "saved across all instances of the class", thus I should be able to instantiate the class with or with out an object passed into the constructor, assume that something is there and get back my array we created on index.php

So my question is:

How does static methods really work in terms of classes? Is there a way to do what I am trying to do with out the use of third party tools if I am just passing objects around?

Answer 1

The static property is static across the same PHP execution. If you run it on index.php, then at the end of execution it is destroyed. On sample.php it will be a new execution. This works as you expect (same execution):

//index.php
class Something{
    protected static $_something = null;

    public function __construct($options = null){
        if(self::$_something === null && $options != null){ 
            self::$_something = $options ;
        }
    }

    public function get_something(){ return self::$_something; }
}

$class_instantiation = new Something(array('test' => 'example'));
var_dump($class_instantiation->get_something());

$class_instantiation2 = new Something();
var_dump($class_instantiation2->get_something());

Both objects dump:

array(1) {
  ["test"]=>
  string(7) "example"
}

Answer 2

static in PHP also means that you could access to property/method without instatiating the class. It's hard to keep static variables across the same PHP execution as, often, your execution will end with a server response but as AbraCadaver says, they act as you expect within the same execution (same request, read that way)