CODEWITHSUNDEEP
phpclassinheritancemethods
JuanBonnett
JuanBonnett

Reputation: 786

Inherit a method without requiring parameters from the parent

I have a class like this

class Parent {

public function add($query = "", $queryParams = []) {
    if(empty($query)) {
        $query = "blablabla";
    }
    if(empty($params)) {
        $params = [blablabla];
    }
    //... some logic;
    //return something;
}

}

and I want to have a Child class like this

class Child extends Parent {

public function add() {
    $query = "blablabla";
    $params = [blablabla];
    return parent::add($query, $params);
}

}

But it always throws me an error saying the child class method must be 'compatible', it means I have to declare the same parameters.

I was thinking of something like declaring a function in the parent like this:

public function __add($query = "", $params = []) {}

and in the child class declare the function like this:

public function add() {
    $query = "blabla"; $params = [blabla]; 
    return parent::__add($query, $params);
}

One problem is that I still need to use some Parent class Objects and the method add(), I not always use only Inherited classes object.

Any ideas?

Upvotes: 0

Views: 160

Answers (1)

georg
georg

Reputation: 214969

Although you could just ignore "strict" messages, this one is given for a reason: changing signatures of parent methods is a Bad Thing, as it violates the famous "Liskov Substitution Principle": a Child class should always be able to replace its Parent. For example, if you have something like

$p = new Parent();
$p->do_this()
$p->and_that()
$p->add(x,y)

and if you replace the first line with

$p = new Child();

the rest of the code should work as before. Obviously, changing the signature will cause it to break.

Create a new method in the Child, e.g. addWithDefaults() or similar, and leave the inherited add() in peace.

Upvotes: 1

Related Questions