Can External Methods Be Included in a PHP Class, and What\'s the Best Alternative?

Including External Methods into a PHP Class

Can code be included into a PHP class?

Including code directly into the body of a class is not possible in PHP. However, methods can be included from external files outside of the class body.

Segregating Business Logic

The desire to separate business logic from other class elements is understandable. However, including methods from a separate file violates PHP syntax rules.

Performance Concerns

If Myclass.php is included only once per request, the external file Myclass_methods.php will also be included only once. Thus, performance should not be a major concern.

Proper Solution: Strategy Pattern

To dynamically change class behavior, the Strategy Pattern is a more suitable approach than including external files. It involves creating an interface with a defined method and implementing multiple classes that conform to the interface with different implementations of the method.

Implementation:

// MeowingInterface.php
interface MeowingInterface
{
    public function meow(): string;
}

// RegularMeow.php
class RegularMeow implements MeowingInterface
{
    public function meow(): string
    {
        return 'meow';
    }
}

// LolcatMeow.php
class LolcatMeow implements MeowingInterface
{
    public function meow(): string
    {
        return 'lolz xD';
    }
}

// Cat.php
class Cat
{
    private MeowingInterface $meowingBehaviour;

    public function setMeowingBehaviour(MeowingInterface $meowingBehaviour): void
    {
        $this->meowingBehaviour = $meowingBehaviour;
    }

    public function meow(): string
    {
        return $this->meowingBehaviour->meow();
    }
}

Usage:

// index.php
require_once 'MeowingInterface.php';
require_once 'RegularMeow.php';
require_once 'LolcatMeow.php';
require_once 'Cat.php';

$cat = new Cat();
$cat->setMeowingBehaviour(new RegularMeow());
echo $cat->meow(); // Outputs "meow"

// Change behaviour
$cat->setMeowingBehaviour(new LolcatMeow());
echo $cat->meow(); // Outputs "lolz xD"

By following the Strategy Pattern, you can easily change the behavior of a class without resorting to unorthodox practices like including external files. This approach provides code flexibility and maintainability in the long run.

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