Here is some clarification about PHP inheritance – there is a lot of bad information on the net.  PHP does support Multi-level inheritance.  (I tested it using version 5.2.9).  It does not support multiple inheritance. This means that you cannot have one class extend 2 other classes (see the extends keyword).  However, you can have one class extend another, which extends another, and so on.  Example: <?phpclass A {        // more code here} class B extends A {        // more code here} class C extends B {        // more code here}  $someObj = new A();  // no problems$someOtherObj = new B(); // no problems$lastObj = new C(); // still no problems ?>

I think the best way for beginners to understand inheritance is through a real example so here is a simple example I can gave to you <?phpclass Person{    public $name;    protected $age;    private $phone;    public function talk(){        //Do stuff here    }    protected function walk(){        //Do stuff here    }    private function swim(){        //Do stuff here    }}class Tom extends Person{    /*Since Tom class extends Person class this means         that class Tom is a child class and class person is         the parent class and child class will inherit all public         and protected members(properties and methods) from        the parent class*/     /*So class Tom will have these properties and methods*/     //public $name;     //protected $age;     //public function talk(){}     //protected function walk(){}     //but it will not inherit the private members      //this is all what Object inheritance means}

The Idea that multiple inheritence is not supported is correct but with tratits this can be reviewed.for e.g. <?phptrait  custom{     public function hello()     {          echo "hello";     }}trait custom2{       public function hello()       {            echo "hello2";       }}class inheritsCustom{        use custom, custom2        {              custom2::hello insteadof custom;        }}$obj = new inheritsCustom();$obj->hello();?>

You can force a class to be strictly an inheritable class by using the "abstract" keyword. When you define a class with abstract, any attempt to instantiate a separate instance of it will result in a fatal error. This is useful for situations like a base class where it would be inherited by multiple child classes yet you want to restrict the ability to instantiate it by itself.Example........<?phpabstract class Cheese{      //can ONLY be inherited by another class}class Cheddar extends Cheese{}$dinner = new Cheese; //fatal error$lunch = new Cheddar; //works!?>

I was recently extending a PEAR class when I encountered a situation where I wanted to call a constructor two levels up the class hierarchy, ignoring the immediate parent.  In such a case, you need to explicitly reference the class name using the :: operator.Fortunately, just like using the 'parent' keyword PHP correctly recognizes that you are calling the function from a protected context inside the object's class hierarchy.E.g:<?phpclass foo{  public function something()  {    echo __CLASS__; // foo    var_dump($this);  }}class foo_bar extends foo{  public function something()  {    echo __CLASS__; // foo_bar    var_dump($this);  }}class foo_bar_baz extends foo_bar{  public function something()  {    echo __CLASS__; // foo_bar_baz    var_dump($this);  }  public function call()  {    echo self::something(); // self    echo parent::something(); // parent    echo foo::something(); // grandparent  }}error_reporting(-1);$obj = new foo_bar_baz();$obj->call();// Output similar to:// foo_bar_baz// object(foo_bar_baz)[1]// foo_bar// object(foo_bar_baz)[1]// foo// object(foo_bar_baz)[1]?>

In case you have a public readonly property in a class you need to extend, adding other properties, this can be a way to do it:<?phpclass A {    public function __construct(        public readonly int $prop    ) {}}class B extends A {    public function __construct(        int $prop,        public readonly int $prop2    ) {        parent::__construct($prop);    }}?>