PHP use abstract class or interface?

Question

In this piece of code is it better to use abstract classes in place of the interfaces or is it good as it currently is? If so, why?

/** contract for all flyable vehicles **/
interface iFlyable {
    public function fly();
}

/* concrete implementations of iFlyable interface */
class JumboJet implements iFlyable {
    public function fly() {
        return "Flying 747!";
    }
}

class FighterJet implements iFlyable {
    public function fly() {
        return "Flying an F22!";
    }
}

class PrivateJet implements iFlyable {
    public function fly() {
        return "Flying a Lear Jet!";
    }
}

/** contract for conrete Factory **/
/**
* "Define an interface for creating an object, but let the classes that implement the interface
* decide which class to instantiate. The Factory method lets a class defer instantiation to
* subclasses."
**/
interface iFlyableFactory {
    public static function create( $flyableVehicle );
}

/** concrete factory **/
class JetFactory implements iFlyableFactory {
    /* list of available products that this specific factory makes */
    private  static $products = array( 'JumboJet', 'FighterJet', 'PrivateJet' );

    public  static function create( $flyableVehicle ) {
        if( in_array( $flyableVehicle, JetFactory::$products ) ) {
            return new $flyableVehicle;
        } else {
            throw new Exception( 'Jet not found' );
        }
    }
}

$militaryJet = JetFactory::create( 'FighterJet' );
$privateJet = JetFactory::create( 'PrivateJet' );
$commercialJet = JetFactory::create( 'JumboJet' );

This is probably better suited for codereview.stackexchange.com — Mike Brant
– Mike Brant, Commented Jan 7, 2015 at 19:51
This is also largely going to be opinion-base as well, but I will give one opinion (not an answer). I think that your example is too simplistic to determine which might be better. If for example there are common behaviors that might exist for all flying vehicles that might lend to better code reuse (i.e. change altitude, change heading, take-off, land) with overriding behaviors only in certain cases, then maybe an abstract class might be preferable to an interface. — Mike Brant
– Mike Brant, Commented Jan 7, 2015 at 19:55

David Chan · Accepted Answer · 2015-01-07 19:54:17Z

4

the interface is more flexible. this way not everything that flies is forced to inherit from the same base class (php doesnt support multiple inheritance)

so

class bird extends animal implements flyable
class plane extends machine implements flyable
class cloud implements flyable

sometimes flexibility is not desired.

abstract classes can also provide function definitions which will reduce code duplication if multiple flying classes required the same fly() method

hope that helps you understand your choice

answered Jan 7, 2015 at 19:54

David Chan

7,5222 gold badges30 silver badges50 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Robert Over a year ago

Makes a lot of sense. Thnaks @David Chan

Collectives™ on Stack Overflow

PHP use abstract class or interface?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related