Private Visibility

The private keyword is part of the three keywords to define visibility of a method, property or constant. It is the strictest level of visibility : it restrict usage to the current class only. Child class can’t redefine it, nor access it.

The private keyword cannot be used with the final keyword : a private method is not visible in the child classes, and can’t also be redefined.

<?php

class x {
    private const X = 1;

    final public function method() {
        echo self::X;
    }
}

?>

Documentation

Related : Final Keyword, Visibility, Protected Visibility, Public Visibility, Var