请看这段代码:classFoo{public$barInstance;publicfunctiontest(){$this->barInstance=newBar();$this->barInstance->fooInstance=$this;$this->barInstance->doSomethingWithFoo();}}classBar{public$fooInstance;publicfunctiondoSomethingWithFoo(){$this->fooInstance->something();}}$foo=newFoo();$foo->test();问题:是否可以