Various uses of PHP's "static" keyword.

PHP-statics.txt

PHP's "statics"

1. Static methods within a class.

Note: Allows dev's to encapsulate similar methods within a class, but with the "benefit" of easy access by means of global scope.
Reference: http://php.net/manual/en/language.oop5.static.php
Example:

class Foo
{
    public static function a_static_method()
    {
        echo 'Hi!';
    }
}

<?php

Foo::a_static_method(); // Prints "Hi!";

2. Static variables

Note: PHP creates an internal memory pointer to the variable marked as static. This means it will survive multiple page reloads giving developer's a little state within a stateless environment (HTTP)
Reference: http://php.net/manual/en/language.variables.scope.php#language.variables.scope.static
Example:

<?php

function foo()
{
	static $a = 0;
	return $a++;
}

echo foo(); // Prints 0, then after reload 1, then 2 (etc)

3. LSB (Late Static Binding)

Note: Allows dev's to define which class should be referred-to by subclasses; One of the base class or the subclass.
Reference: http://php.net/manual/en/language.oop5.late-static-bindings.php
Example: (See reference page)

Note also the use of `new static()` which allows instantiating classes within static methods.