php中的匿名函数和闭包(closure)

这个是我在博客园上写的一篇文章，我的博客园blog地址：http://www.cnblogs.com/starlion 一：匿名函数 ( 在php5.3.0 或以上才能使用 ) php中的匿名函数(Anonymous functions)， 也叫闭包函数( closures ), 允许指定一个没有名称的函数。最常用的就是回调函

这个是我在博客园上写的一篇文章，我的博客园blog地址：http://www.cnblogs.com/starlion

一：匿名函数 (在php5.3.0 或以上才能使用)

     php中的匿名函数(Anonymous functions)， 也叫闭包函数(closures), 允许指定一个没有名称的函数。最常用的就是回调函数的参数值。（http://php.net/manual/zh/functions.anonymous.php）

     匿名函数的定义：

<span>$closureFunc</span> = <span>function</span><span>(){

　　　　</span>....<span>

 };</span>

   eg: 把匿名函数赋值给变量，通过变量来调用

 <span>$closureFunc</span> = <span>function</span>(<span>$str</span><span>){

　　 </span><span>echo</span> <span>$str</span><span>;

  };

  </span><span>$closureFunc</span>("hello world!");

  输出： hello world!

 

二：闭包

 2.1  将匿名函数放在普通函数中，也可以将匿名函数返回，这就构成了一个简单的闭包 

<span>function</span><span> closureFunc1(){
    </span><span>$func</span> = <span>function</span><span>(){
        </span><span>echo</span> "hello"<span>;
    };
    </span><span>$func</span><span>();
}
closureFunc1();
</span><span>//</span><span>输出: hello</span>

2.2  在匿名函数中引用局部变量

<span>function</span><span> closureFunc2(){
    </span><span>$num</span> = 1<span>;
    </span><span>$func</span> = <span>function</span><span>(){
        </span><span>echo</span> <span>$num</span><span>;
    };
    </span><span>$func</span><span>();
}
closureFunc2();
</span><span>//</span><span>Notice: Undefined variable: num</span>

上面的函数运行后，会报Notice错误，说明我们不能在匿名函数中这样使用局部变量，这时候就要引用一个php的关键字 use， 代码如下

<span>function</span><span> closureFunc2(){
    </span><span>$num</span> = 1<span>;
    </span><span>$func</span> = <span>function</span>() <span>use</span>(<span>$num</span><span>){
        </span><span>echo</span> <span>$num</span><span>;
    };
    </span><span>$func</span><span>();
}
closureFunc2();
</span><span>//</span><span>输出: 1</span>

 2.3  返回匿名函数

<span>function</span><span> closureFunc3(){
    </span><span>$num</span> = 1<span>;
    </span><span>$func</span> = <span>function</span>() <span>use</span>(<span>$num</span><span>){
        </span><span>echo</span> <span>$num</span><span>;
    };
    </span><span>return</span> <span>$func</span><span>;
}
</span><span>$func</span> =<span> closureFunc3(); //函数返回匿名函数
</span><span>$func</span><span>(); //然后我们在用$func() 调用
</span><span>//</span><span>输出: 1</span>

2.4 当我们在返回匿名函数时候怎么给匿名函数传参呢？ 其实跟普通函数传参数一样

<span>function</span><span> closureFunc4(){
    </span><span>$num</span> = 1<span>;
    </span><span>$func</span> = <span>function</span>(<span>$str</span>) <span>use</span>(<span>$num</span><span>){
        </span><span>echo</span> <span>$num</span><span>;
        </span><span>echo</span> "\n"<span>;
        </span><span>echo</span> <span>$str</span><span>;
    };
    </span><span>return</span> <span>$func</span><span>;
}
</span><span>$func</span> =<span> closureFunc4();
</span><span>$func</span>("hello, closure4"<span>);
</span><span>//</span><span>输出:
//1
//hello, closure4</span>

2.5 怎么用闭包来改变上下文引用的变量值？

<span>function</span><span> closureFunc5(){
    </span><span>$num</span> = 1<span>;
    </span><span>$func</span> = <span>function</span>() <span>use</span>(<span>$num</span><span>) {
        </span><span>echo</span> "\n"<span>;
        </span><span>$num</span>++<span>;
        </span><span>echo</span> <span>$num</span><span>;
    };
    </span><span>echo</span> "\n"<span>;
    </span><span>echo</span> <span>$num</span><span>;
    </span><span>return</span> <span>$func</span><span>;
}
</span><span>$func</span> =<span> closureFunc5();
</span><span>$func</span><span>();
</span><span>$func</span><span>();
</span><span>$func</span><span>();
</span><span>//</span><span>输出:
// 1
// 2
// 2
// 2</span>

看上面的输入结果，显然没有达到目的， 其实只要加一个 & 引用符号就可以了

<span>function</span><span> closureFunc5(){
    </span><span>$num</span> = 2<span>;
    </span><span>$func</span> = <span>function</span>() <span>use</span>(&<span>$num</span><span>) {
        </span><span>echo</span> "\n"<span>;
        </span><span>$num</span>++<span>;
        </span><span>echo</span> <span>$num</span><span>;
    };
    </span><span>echo</span> "\n"<span>;
    </span><span>echo</span> <span>$num</span><span>;
    </span><span>return</span> <span>$func</span><span>;
}
</span><span>$func</span> =<span> closureFunc5();
</span><span>$func</span><span>();
</span><span>$func</span><span>();
</span><span>$func</span><span>();
</span><span>//</span><span>输出:
// 2
// 3
// 4
// 5</span>

2.6 把匿名函数当作参数传递

<span>function</span> callFunc(<span>$func</span><span>){
    </span><span>$func</span>("argv"<span>);
}

callFunc(</span><span>function</span>(<span>$str</span><span>){
    </span><span>echo</span> <span>$str</span><span>;
})
</span><span>//</span><span>输出：
// argv</span>

 

参考：

http://www.cnblogs.com/yjf512/archive/2012/10/29/2744702.html 为什么要引入闭包

http://blog.csdn.net/lgg201/article/details/6127564  php 5.3.0 的function() use() {}