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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:<?phpclassA{// more code here} classBextendsA{// more code here} classCextendsB{// more code here}$someObj= newA();// no problems$someOtherObj= newB();// no problems$lastObj= newC();// 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<?phpclassPerson{    public$name;    protected$age;    private$phone;    public functiontalk(){//Do stuff here}    protected functionwalk(){//Do stuff here}    private functionswim(){//Do stuff here}}classTomextendsPerson{/*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}

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:<?phpclassA{    public function__construct(        public readonlyint $prop) {}}classBextendsA{    public function__construct(int $prop,        public readonlyint $prop2) {parent::__construct($prop);    }}?>

The Idea that multiple inheritence is not supported is correct but with tratits this can be reviewed.for e.g.<?phptraitcustom{     public functionhello()     {          echo"hello";     }}traitcustom2{       public functionhello()       {            echo"hello2";       }}classinheritsCustom{        usecustom,custom2{custom2::helloinsteadofcustom;        }}$obj= newinheritsCustom();$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 classCheese{//can ONLY be inherited by another class}classCheddarextendsCheese{}$dinner= newCheese;//fatal error$lunch= newCheddar;//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:<?phpclassfoo{  public functionsomething()  {    echo__CLASS__;// foovar_dump($this);  }}classfoo_barextendsfoo{  public functionsomething()  {    echo__CLASS__;// foo_barvar_dump($this);  }}classfoo_bar_bazextendsfoo_bar{  public functionsomething()  {    echo__CLASS__;// foo_bar_bazvar_dump($this);  }  public functioncall()  {    echoself::something();// selfechoparent::something();// parentechofoo::something();// grandparent}}error_reporting(-1);$obj= newfoo_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]?>