Question

I want to add additional stuff to the parent class.
I can’t modify the parent class because all modifications will be erased when the software is upgraded. So I want to extend the class. Can I just add this in the child class without repeating parent functions?

class parent
{
    public function __construct()
    {
        // lots of logic to hook up following functions with main software
    }

      // lots of parent functions
}

class child extends parent
{
     function __construct()
    {
        // Is this going to share parent's logic and hook up with those actions?
        // Or, should I repeat those logics?
        parent::__construct();

        // add child addicional logic
    }
     // child functions
    // should I repeat parent's functions? I need the parent take child along all the jobs.

}

Answer 1

Yes, that is the correct way to do it.

class parent
{
    public function __construct()
    {
        // lots of logic to hook up following functions with main software
    }
    // lots of parent functions

    protected function exampleParentFunction()
    {
        //do lots of cool stuff
    }
}

class child extends parent
{
     function __construct()
    {
        // This will run the parent's constructor
        parent::__construct();
        // add child additional logic
    }
    // child functions
    public function exampleChildFunction();
    {
        $result = $this->exampleParentFunction();
        //Make result even cooler :)
    }
    //or you can override the parent methods by declaring a method with the same name
    protected function exampleParentFunction()
    {
        //use the parent function
        $result = parent::exampleParentFunction();
        //Make result even cooler :)
    }
}

Going by your recent questions you really need to read a book on PHP OOP. Start with the manual http://www.php.net/oop