static variable php

1<?php
2class Car
3{
4    public function test($var = 'Hello kinjal')
5    {
6        $this->var = $var;
7        return $this->var;
8    }
9}
10class Bike
11{
12    public static function test($var)
13    {
14        $var = '<br>this is static function';
15        return $var;
16    }
17}
18$obj = new Car();
19echo $obj->test();
20echo Bike::test('this is non static');      //static function called using :: double colon
21
22?>

1
2<?php
3function foo(){
4    static $int = 0;          // correct 
5    static $int = 1+2;        // correct
6    static $int = sqrt(121);  // wrong  (as it is a function)
7
8    $int++;
9    echo $int;
10}
11?>
12
13