Static Function Demo

<?php

class DoMath {
    public $var;
    public static $boo;
    
    public function addToVar($value) {
        // $this->var += $value;
    }
    
    public static function add($valueA, $valueB) {
        return $valueA + $valueB;
    }
    
    public static function addToIt($value) {
        static::$boo += $value;
    }
}

$obj = new DoMath();

$obj->var = 5;

var_dump($obj->var);

$obj->addToVar(7);

var_dump($obj->var);

var_dump(DoMath::add(9, 2));

var_dump(DoMath::addToIt(4));