Several ways to call parent method in php

Question

At first I was confused why both methods called in the constructor, but now I think I understand. Extending classes inherit parent methods as if they were declared in the class itself. And the methods exist in the parent, so both should work.

Now I am wondering if there is a preferred way (for example, a better way) to call a method (via parent or this ) and whether these are really identical ways to execute the same code or if there are any caveats when using one over the other .

Sorry, I probably thought about that.

 abstract class Animal { function get_species() { echo "test"; } } class Dog extends Animal { function __construct(){ $this->get_species(); parent::get_species(); } } $spike = new Dog; 

Answer 1

There are three scenarios (I can think of) in which you would call a method in a subclass where the method leaves the parent class:

• The method is not overwritten by a subclass; it exists only in the parent.

  This is the same as your example, and generally it is better to use $this -> get_species(); . You are right that in this case the two are practically the same, but the method was inherited by a subclass, so there is no reason to differentiate. Using $this , you remain consistent between legacy methods and locally declared methods.

• The method is overwritten by a subclass and has completely unique logic from the parent.

  In this case, you obviously want to use $this -> get_species(); because you do not want the parent version of the method to be executed. Again, sequentially using $this , you don’t have to worry about the difference between this case and the first.

• The method extends the parent class, adding to what the parent method reaches.

  In this case, you still want to use `$this -> get_species(); when calling a method from other methods of the subclass. One place you call the parent method will be from the method that overrides the parent method. Example:

   abstract class Animal { function get_species() { echo "I am an animal."; } } class Dog extends Animal { function __construct(){ $this->get_species(); } function get_species(){ parent::get_species(); echo "More specifically, I am a dog."; } } 

The only scenario I can imagine when you would need to call the parent method directly outside the override method would be if they did two different things, and you knew that you needed the parent version of the method, not the local one. This should not be so, but if it were by itself, then an easy way to approach this is to create a new method with a name like get_parentSpecies() , where all it does is call the parent method:

 function get_parentSpecies(){ parent::get_species(); } 

Again, this keeps everything nice and consistent, which allows you to change / change the local method, rather than relying on the parent method.

Answer 2

If I do not understand the question, I will almost always use $ this-> get_species, because a subclass (in this case a dog) can overwrite this method as it extends it. If the class dog does not override the method, then both methods are functionally equivalent, but if at some point in the future you decide that you want the get_species method on the dog to print "dog", you would need to go through all the code and Change this.

When you use $ this, this is actually part of the object you created, and therefore will always be the very last one (if the used property has somehow changed during the life of the object), while using the parent class calls the static class method.