Can I instantiate a PHP class inside another class?

Question

I was wondering if it is allowed to create an instance of a class inside another class.

Or, do I have to create it outside and then pass it in through the constructo

Answer 1

It's impossible to create a class in another class in PHP. Creating an object(an instance of a class) in another object is a different thing.

Answer 2

This is possible in PHP 7 with Anonymous classes.

See the example from the docs:

class Outer
{
    private $prop = 1;
    protected $prop2 = 2;

    protected function func1()
    {
        return 3;
    }

    public function func2()
    {
        return new class($this->prop) extends Outer {
            private $prop3;

            public function __construct($prop)
            {
                $this->prop3 = $prop;
            }

            public function func3()
            {
                return $this->prop2 + $this->prop3 + $this->func1();
            }
        };
    }
}

echo (new Outer)->func2()->func3();
// Output: 6

This is a simple example showing usage of anonymous classes, but not from within a class:

// Pre PHP 7 code
class Logger
{
    public function log($msg)
    {
        echo $msg;
    }
}

$util->setLogger(new Logger());

// PHP 7+ code
$util->setLogger(new class {
    public function log($msg)
    {
        echo $msg;
    }
});