<?php
class MethodVisiblity
{
    private $name = "parent";
 
    public function __construct()
    {
        $this->privateFunction($this->name);
        $this->protectedFunction($this->name);
        $this->publicFunction($this->name);
    }
 
    private function privateFunction($at)
    {
        echo $this->name." : privateFunction @ : ".$at."\n";
    }
 
    protected function protectedFunction($at)
    {
        echo $this->name." : protectedFunction @ : ".$at."\n";
    }
 
    public function publicFunction($at)
    {
        echo $this->name." : publicFunction @ : ".$at."\n";
    }
}
 
class Extension extends MethodVisiblity
{
    private $name = "child";
 
    public function __construct()
    {
        //$this->privateFunction($this->name); //Fatal error: Call to private method MethodVisiblity::privateFunction() from context 'Extension'
        $this->protectedFunction($this->name);
        $this->publicFunction($this->name);
    }
}
 
$var = new MethodVisiblity();
$child = new Extension();

parent : privateFunction @ : parent
parent : protectedFunction @ : parent
parent : publicFunction @ : parent
parent : protectedFunction @ : child //親のメソッドが子で実行されるので、こうなる。
parent : publicFunction @ : child