PHP Overriding methods rules

Question

I just read from the book:
"In PHP 5, except for constructors, any derived class must use the same signature when overriding a method"
From the PHP manual in the comments:
"In the overriding, the method names and arguments (arg’s) must be same.
Example:
class P { public function getName(){} }
class C extends P{ public function getName(){} } "

So why I'm able to replace method with other arguments and their quantity? Is this legal or will trigger errors in the future or I'm just missing something?

PHP Version 5.5.11

class Pet {
    protected $_name;
    protected $_status = 'None';
    protected $_petLocation = 'who knows';

// Want to replace this function
    protected function playing($game = 'ball') {
        $this->_status = $this->_type . ' is playing ' . $game;
        return '<br>' . $this->_name . ' started to play a ' . $game;
    }

    public function getPetStatus() {
        return '<br>Status: ' . $this->_status;
    }
}


class Cat extends Pet {

    function __construct() {
        $this->_type = 'Cat';
        echo 'Test: The ' . $this->_type . ' was born ';
    }

// Replacing with this one    
    public function playing($gameType = 'chess', $location = 'backyard') {
        $this->_status = 'playing ' . $gameType . ' in the ' . $location;
        return '<br>' . $this->_type . ' started to play a ' . $gameType . ' in the ' . $location;
    }
}

$cat = new Cat('Billy');
echo $cat->getPetStatus();
echo $cat->playing();
echo $cat->getPetStatus();

This will output:

Test: The Cat was born
Status: None
Cat started to play a chess in the backyard
Status: playing chess in the backyard

Turn on error displaying and set error level to E_ALL

sectus
– sectus

2014-06-28 02:51:04 +00:00
Commented Jun 28, 2014 at 2:51 — sectus
– sectus, Commented Jun 28, 2014 at 2:51
Nothing really happened, it's shows no errors.

ProgZi
– ProgZi

2014-06-28 02:57:04 +00:00
Commented Jun 28, 2014 at 2:57 — ProgZi
– ProgZi, Commented Jun 28, 2014 at 2:57

Ja͢ck · Accepted Answer · 2021-05-07 09:45:51Z

14

The rule is that a method signature must be compatible with the method it overrides. Let's look at the two methods in your hierarchy:

protected function playing($game = 'ball');

public function playing($gameType = 'chess', $location = 'backyard');

The changes:

Visibility: protected -> public; increasing the visibility is compatible (the opposite will cause errors).
Arguments: no change (same number of required arguments and maximum number of arguments)

edited May 7, 2021 at 9:45

answered Jun 28, 2014 at 3:14

Ja͢ck

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2 Comments

Daniyal Nasir Over a year ago

I tried and got this error Declaration of ChildController::test($p1) should be compatible with ParentController::test($p1, $p2 = NULL), so thought I might add that It seems that a child must have minimum no. of arguments as its parent counterpart (or more / or optional but identical in number) @Jack Can you second me ?

Ja͢ck Over a year ago

@DaniyalNasir that's because your child method can't be called with 2 arguments, hence it's not compatible

Community · Accepted Answer · 2017-05-23 12:29:26Z

5

PHP does not support overloading in the way you are describing it. However, the parameters must only be of the same type (i.e. integers, strings, arrays, etc). You may have additional parameters that are specific to the overriding method, but the initial parameters MUST match those of the parent class.

This may also be a duplicate of PHP function overloading.

edited May 23, 2017 at 12:29

CommunityBot

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answered Jun 28, 2014 at 3:07

jsickles

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