Can PHP Classes Include Code Directly, and What Are Better Alternatives?

Can You Include Code Within a PHP Class?

PHP class definitions require specific syntax, and including code directly into the class body is not permitted. Including files within a class definition is allowed, but only outside the class body or inside method bodies.

Separating Class Behavior

To separate the class definition from its behavior, you could use an unconventional approach:

class MyClass
{
    // Class definition
    
    public function __construct()
    {
        // Include methods from external file
        include('Myclass_methods.php');
    }
}

Note that this approach includes methods within a method scope, not the class scope itself.

Limitations of Including Files

Direct inclusion of methods within the class body is prohibited. Patching the class dynamically to change its behavior using includes is also not a recommended practice.

Interface and Strategy Pattern

A better solution to dynamically modify class behavior is to use an interface and implement the Strategy pattern. Define an interface for common behavior, implement different Meowing strategies, and then allow your class to switch between these strategies:

interface Meowing
{
    public function meow();
}

class RegularMeow implements Meowing
{
    public function meow()
    {
        return 'meow';
    }
}

class LolkatMeow implements Meowing
{
    public function meow()
    {
        return 'lolz xD';
    }
}

class Cat
{
    private Meowing $meowing;

    public function setMeowing(Meowing $meowing)
    {
        $this->meowing = $meowing;
    }

    public function meow()
    {
        return $this->meowing->meow();
    }
}

This approach allows you to dynamically change the behavior of your class by switching the implemented Meowing strategy.

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