`static` keyword inside function?

Question

I was looking at the source for Drupal 7, and I found some things I hadn\'t seen before. I did some initial looking in the php manual, but it didn\'t explain these examples.

Answer 1

To expand on the answer of Yang

If you extend a class with static variables, the individual extended classes will hold their "own" referenced static that's shared between instances.

<?php
class base {
     function calc() {
        static $foo = 0;
        $foo++;
        return $foo;
     }
}

class one extends base {
    function e() {
        echo "one:".$this->calc().PHP_EOL;
    }
}
class two extends base {
    function p() {
        echo "two:".$this->calc().PHP_EOL;
    }
}
$x = new one();
$y = new two();
$x_repeat = new one();

$x->e();
$y->p();
$x->e();
$x_repeat->e();
$x->e();
$x_repeat->e();
$y->p();

outputs:

one:1
two:1
one:2
one:3 <-- x_repeat
one:4
one:5 <-- x_repeat
two:2

http://ideone.com/W4W5Qv