1. JAVASCRIPT: a. 代码:
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
  1. PHP: a. 代码:
<?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