Given class MyClass with static property $var:

class MyClass
{
    public static $var = 42;
}

To access MyClass::$var in class method method():

class MyClass
{
    public static $var = 42;

    public function method()
    {
        self::$var;
    }
}

Notice how the syntax is self::$var.

To access a class property when it’s not static:

class MyClass
{
    public $var = 42;

    public function method()
    {
        $this->var;
    }
}

Notice how the syntax is $this->var.

See static properties for more details.