依赖于另一个类的PHP类

class ClassA {
    private $dependency;

    public function __construct(ClassB $dependency) {
        $this->dependency = $dependency;
    }
}

$dependency = new ClassB();
$classA = new ClassA($dependency);

class ClassA {
    private $dependency;

    public function setDependency(ClassB $dependency) {
        $this->dependency = $dependency;
    }
}

$dependency = new ClassB();
$classA = new ClassA();
$classA->setDependency($dependency);

class ClassA {
    private $dependency;

    public function setDependency(ClassB $dependency) {
        $this->dependency = $dependency;
    }
}

$dependency = new ClassB();
$classA = new ClassA();
$classA->setDependency($dependency);