PHP类在多个声明上的性能

Question

Let's say I have a huge class named Foo. if I have to call this class several times in different classes, what is the best way to use it?

Note: Bar is not the only class that will use Foo.

Option #1 (create object when its needed):

class Bar
{
    public function myMethod($arg)
    {
        $foo = new Foo();
        $something = $foo->doSomething($arg);

        return $something;
    }
}

Option #2 (create it once):

class Bar
{
    protected $foo;

    public function __construct()
    {
        $this->foo = new Foo();
    }
}

Option #3 (make Foo static):

class Bar
{
    public function myMethod($arg)
    {
        return Foo::doSomething($arg);
    }
}

Option #4:

// tell me the proper way to do it

Answer 1

The best way I'd say is to instantiate Foo outside the Bar class and inject it as a dependency - the best way to do this would be via constructor:

class Bar
{
    private $foo;

    public function __construct(Foo $foo)
    {
        $this->foo = foo;
    }
}

$foo = new Foo();
$bar = new Bar($foo);

Then do the same for all classes that have Foo as a dependency. You can reuse the instance if it is suitable or you can create a new one if needed.