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php中include()和require()以及include_once()和require_once()的区别

2024-07-27 21:50:01
php中include()和require()以及include_once()和require_once()的区别

4者都有包含文件的意思,但include()和include_once()在包含文件出错时程序会继续往下执行,而require()和require_once()则不会,另外include_once()和require_once()只包含一次,多余的不会被包含进来。例子:

<?php

$a=5;

//include('./test.php');//test.php中代码为$a+=3;

//require('./test.php');

//echo $a;//结果为8;

//包含不存在的文件test1.php时

//include('./test1.php');//结果提示warning,并输出5;

//require('./test1.php');//结果提示错误fatal error并停止程序往下执行

//echo $a;

include_once('./test.php');
include_once('./test.php');
include_once('./test.php');
include_once('./test.php');
echo $a;

//结果输出8,因为include_once()或者require_once()如果有多个,只会执行第一个。而include()或者require()如果有多个则会全部执行