javascript与php观察者模式

var a = function(){
this.int = 0
this.add = function(int){
    this.int = int
}
this.watch = function(){
    if(this.int==0){
        console.log('0')
    }else{
        console.log('not 0')
    }
}
}
var a = new a()
a.watch()
a.add(1)
a.watch()

b. 输出：

0
not 0

<?php
class a{
public $int = 0;
public function add($int){
    $this->int += $int;
}
public function watch(){
    if($this->int==0){
        echo "0".PHP_EOL;
    }else{
        echo "not 0".PHP_EOL;
    }
}
}
$a = new a();
$a->watch();
$a->add(1);
$a->watch();

b. 输出：

0
not 0