PHP uses func_get_arg, func_get_args, func_num_args to implement pseudo-overloading_PHP tutorial

php uses func_get_arg, func_get_args, func_num_args to implement pseudo-overloading

Occasionally I saw the issue about pseudo-overloading of php on the Internet, and I was interested and studied it. The author below will talk about how PHP uses func_get_arg, func_get_args, and func_num_args to implement pseudo-overloading of functions.

First let’s talk about the benefits of method overloading:

To implement method overloading, you don’t have to write multiple functions for different parameter types or number of parameters. Multiple functions use the same name, but the parameter list, that is, the number of parameters or (and) data type, can be different. When calling, although the method name is the same, the corresponding function can be automatically called according to the parameter list. If we use reflector to check the .net base class library written by Microsoft, we can find that it uses a lot of method overloading, so that when we call it, we don’t need to remember so many method names, but know the method The function can directly pass different parameters to it, and the compiler will clearly know which method we called.

But there is no concept of function overloading in PHP, which makes it impossible for us to perform some processing in many cases. Sometimes we even have to define N parameters after the function to solve related problems. PHP provides several functions, such as: func_get_arg, func_get_args, func_num_args can directly solve related problems. A specific example code is as follows:

<?php
function  testOne($a) {
echo ('一个参数就这样 ');
}
function testTwo($a, $b) {
	echo ('两个参数的就这样 ');
}
function testThree($a, $b, $c) {
	echo ('呵呵，这是三个参数的 ');
}
function test() {
	$argNum = func_num_args();
	// 这一段其实可以用 $_arg = func_get_args() 来获得所有的参数，只是要用数组而已，不方便我下面的表达，呵呵
	for ($i = 0; $i < $argNum; $i++) {
		$_arg_{$i} = func_get_arg($i);
	}
	switch ($argNum) {
		case 1 :
			testOne($_arg_1);
		break ;
		case 2 :
			testTwo($_arg_1, $_arg_2);
		break ;
		case 3 :
			testThree($_arg_1, $_arg_2, $_arg_3);
		break ;
		default :
			echo (' 这是没有参数的情况 ');
		break ;
	}
}
/**
 * 例子的实现
 */
test();
echo ('<br>');
test(1);
echo ('<br>');
test(1, 2);
echo ('<br>');
test(1, 2, 3);
// 这些只是在函数中的运用，其实最主要的还是在类中的运用
// 如果这些用到类里面我就不需要担心构造函数是否有几个参数了，不是吗？
// 类里面的运用只举一个简单的例子
class test{
	var $a = 0;
	var $b = 0;
	function test() {
		$argNum = func_num_args();
		$_arg = func_get_args();
		switch ($argNum) {
			case 1 :
				$this->test1($_arg[0]);
			break ;
			case 2 :
				$this->test2($_arg[0], $_arg[1]);
			break;
			default :
				$this->a = 0;
				$this->b = 1;
			break;
		}
	}
	function test1($a) {
		$this->a = $a;
	}
	function test2($a, $b) {
		$this->a = $a;
		$this->b = $b ;
	}
}

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