<?php
class Visiblity
{
    public $name = "parent";
 
    private $istr1 = "private string.\n";
    protected $istr2 = "protected string.\n";
    public $istr3 = "public string.\n";
 
    private static $sstr1 = "private static string.\n";
    protected static $sstr2 = "protected static string.\n";
    public static $sstr3 = "public static string.\n";
 
    //クラス内からは全部のインスタンス変数にアクセスできるはず。
    public function checkInstance()
    {
        echo "\n";
        echo $this->name." checkInstance\n";
        echo $this->istr1;
        echo $this->istr2;
        echo $this->istr3;
    }
 
    //クラス変数も同様のはず。
    public function checkStatic()
    {
        echo "\n";
        echo $this->name." checkStatic\n";
        echo self::$sstr1;
        echo self::$sstr2;
        echo self::$sstr3;
    }
}
 
class Extension extends Visiblity
{
    public $name = "child";
 
    //親のprivateは見れないはず。
    public function checkParent()
    {
        echo "\n";
        echo $this->name." checkParent\n";
        //echo $this->istr1; //Notice: Undefined property: Extension::$istr1
        echo $this->istr2;
        echo $this->istr3;
    }
 
    //親のprivateは見れないはず。
    public function checkParentStatic()
    {
        echo "\n";
        echo $this->name." checkParentStatic\n";
        //echo parent::$sstr1; //Fatal error: Cannot access private property Visiblity::$sstr1
        echo parent::$sstr2;
        echo parent::$sstr3;
    }
}
 
//echo Visiblity::$sstr1; //Fatal error: Cannot access private property Visiblity::$sstr1
//echo Visiblity::$sstr2; //Fatal error: Cannot access protected property Visiblity::$sstr2
echo Visiblity::$sstr3;
 
 
$var = new Visiblity();
//echo $var->istr1; //Fatal error: Cannot access private property PropertyVisiblity::$istr1
//echo $var->istr2; //Fatal error: Cannot access protected property PropertyVisiblity::$istr2
echo $var->istr3; //public string.
 
$var->checkInstance();
$var->checkStatic();
 
$child = new Extension();
$child->checkInstance();
$child->checkStatic();
 
$child->checkParent();
$child->checkParentStatic();

public static string.
    public string.
 
    parent checkInstance
    private string.
    protected string.
    public string.
 
    parent checkStatic
    private static string.
    protected static string.
    public static string.
 
    child checkInstance
    private string.
    protected string.
    public string.
 
    child checkStatic
    private static string.
    protected static string.
    public static string.
 
    child checkParent
    protected string.
    public string.
 
    child checkParentStatic
    protected static string.
    public static string.