php学习笔记_函数类型

传变量传引用的区别
传引用如:

<code><span>$num</span> = <span>0</span>;
        <span><span>function</span><span>test0</span><span>(<span>$num</span>)</span>{</span><span>//将变量的值副本传进去，而不是变量本身。</span><span>$num</span> = <span>123</span>;
            <span>echo</span><span>$num</span>;
        }
        test0(<span>$num</span>);<span>//输出：123</span><span>echo</span><span>$num</span>; <span>//输出：0</span><span>$num2</span> = <span>100</span>;
        <span><span>function</span><span>test1</span><span>(&<span>$val</span>)</span>{</span><span>//传变量地址，操作的是变量本身</span><span>$val</span> = <span>300</span>;
            <span>echo</span><span>$val</span>;
        }
        test1(<span>$num2</span>);<span>//输出：300</span><span>echo</span><span>$num2</span>;  <span>//输出：300</span></code>

变量函数，即函数名是一个变量

<code><span>$temp</span> = <span>"king"</span>;
    <span>$name</span> = <span>"md5"</span>;
    <span>echo</span><span>$name</span>(<span>$temp</span>);<span>//调用md5方法，将king转成md5    </span></code>

回调函数，一个函数调用另一个函数，但是通过变量函数调用的方法实现，系统提供两个方法：call_user_func()、call_user_func_array()，两者的区别是前者参数是一个一个传，后者参数以数组的形式传。例子如下：

<code><span><span>function</span><span>sayName</span><span>(<span>$val</span>)</span>{</span><span>echo</span><span>"My name is {$val}"</span>;
    }

    <span><span>function</span><span>doWhat</span><span>(<span>$myFunction</span>,<span>$name</span>)</span>{</span><span>$myFunction</span>(<span>$name</span>);
    }

    <span>$name</span> = <span>"King"</span>;
    doWhat(<span>"sayName"</span>,<span>$name</span>）；<span>//输出：My name is King.</span></code>

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