PHP函数处理函数实例详解

1. call_user_func和call_user_func_array: 

以上两个函数以不同的参数形式调用回调函数。见如下示例：

<?php
class AnotherTestClass {
    public static function printMe() {
        print "This is Test2::printSelf.\n";
    }
    public function doSomething() {
        print "This is Test2::doSomething.\n";
    }
    public function doSomethingWithArgs($arg1, $arg2) {
        print 'This is Test2::doSomethingWithArgs with ($arg1 = '.$arg1.' and $arg2 = '.$arg2.").\n";
    }
}

$testObj = new AnotherTestClass();
call_user_func(array("AnotherTestClass", "printMe"));
call_user_func(array($testObj, "doSomething"));
call_user_func(array($testObj, "doSomethingWithArgs"),"hello","world");
call_user_func_array(array($testObj, "doSomethingWithArgs"),array("hello2","world2"));

运行结果如下：

bogon:TestPhp$ php call_user_func_test.php
This is Test2::printSelf.
This is Test2::doSomething.
This is Test2::doSomethingWithArgs with ($arg1 = hello and $arg2 = world).
This is Test2::doSomethingWithArgs with ($arg1 = hello2 and $arg2 = world2).

2. func_get_args、func_num_args和func_get_args：

这三个函数的共同特征是都很自定义函数参数相关，而且均只能在函数内使用，比较适用于可变参数的自定义函数。他们的函数原型和简要说明如下：
int func_num_args (void) 获取当前函数的参数数量。
array func_get_args (void) 以数组的形式返回当前函数的所有参数。
mixed func_get_arg (int $arg_num) 返回当前函数指定位置的参数，其中0表示第一个参数。

<?php
function myTest() {
    $numOfArgs = func_num_args();
    $args = func_get_args();
    print "The number of args in myTest is ".$numOfArgs."\n";
    for ($i = 0; $i < $numOfArgs; $i++) {
        print "The {$i}th arg is ".func_get_arg($i)."\n";
    }
    print "\n-------------------------------------------\n";
    foreach ($args as $key => $arg) {
        print "$arg\n";
    }
}

myTest('hello','world','123456');

运行结果如下：

Stephens-Air:TestPhp$ php class_exist_test.php
The number of args in myTest is
The 0th arg is hello
The 1th arg is world
The 2th arg is 

-------------------------------------------
hello
world

3. function_exists和register_shutdown_function：

    函数原型和简要说明如下：

bool function_exists (string $function_name) 判断某个函数是否存在。
void register_shutdown_function (callable $callback [, mixed $parameter [, mixed $... ]]) 在脚本结束之前或者是中途调用exit时调用改注册的函数。另外，如果注册多个函数，那么他们将会按照注册时的顺序被依次执行，如果其中某个回调函数内部调用了exit()，那么脚本将立刻退出，剩余的回调均不会被执行。

<?php
function shutdown($arg1,$arg2) {
    print '$arg1 = '.$arg1.', $arg2 = '.$arg2."\n";
}

if (function_exists('shutdown')) {
    print "shutdown function exists now.\n";
}

register_shutdown_function('shutdown','Hello','World');
print "This test is executed.\n";
exit();
print "This comments cannot be output.\n";

运行结果如下：

Stephens-Air:TestPhp$ php call_user_func_test.php
shutdown function exists now.
This test is executed.
$arg1 = Hello, $arg2 = World