gistfile1.php

<?php

class Base { 
    function __construct() { 
        $this->foo(); 
    } 

    private function foo() {
        echo 'foo';
    } 
}

class Sub extends Base { 
    private function foo() { 
        echo 'lel'; 
    } 

    public function test() { 
        $this->foo(); 
    } 
}

$sub = new Sub; // foo
$sub->test(); // lel