What is the difference between static and non-static declaration of variables in PHP classes?

Static variables in PHP classes are shared among all instances of that class, while non-static variables are unique to each instance. When declaring a variable as static in a class, it means that the variable belongs to the class itself, not to any specific instance of the class. Non-static variables are specific to each object created from the class. 

<?php
class MyClass {
    public static $staticVar = 0;
    public $nonStaticVar = 0;

    public function incrementStaticVar() {
        self::$staticVar++;
    }

    public function incrementNonStaticVar() {
        $this->nonStaticVar++;
    }
}

$obj1 = new MyClass();
$obj2 = new MyClass();

$obj1->incrementStaticVar();
$obj1->incrementNonStaticVar();

$obj2->incrementStaticVar();
$obj2->incrementNonStaticVar();

echo MyClass::$staticVar; // Output: 2
echo $obj1->nonStaticVar; // Output: 1
echo $obj2->nonStaticVar; // Output: 1
?>

Keywords

static non-static variables declaration PHP classes

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