Difference:
require_once will only load the same file once, while require will load multiple times.
I believe that novices like me still have some doubts. So we guessed: If 456.php introduced 123.php, now the file test_require.php introduces "456.php" and "123.php". If the require method is used, then in test_require.php, 123.php will be introduced twice, and using the require_once method 123.php will be introduced once. So let’s do the experiment!
1. require method
123.php content is as follows:
<?php echo "123\n";
456.php content is as follows:
<?php <span style="white-space:pre"> require("123.php"); <span style="white-space:pre"> </span>echo "456\n";test_require.php The content is as follows:
<?php require("123.php"); require("456.php");runs test_require.php and gets the following results:
2. require_once method
123.php content remains unchanged. 456.php and test_require.php change the require_once method. The content is as follows:
//456.php <?php require_once "123.php"; echo "456\n"; //test_require.php <?php require_once "123.php"; require_once "456.php";runs test_require.php, the results are as follows:
3. Mixing error
If the require method is used in 456.php, and the require_once method is used, then require_once will will fail. The codes of the three files are as follows:
//123.php <?php echo "123\n"; //456.php The running results are as follows:
Summary: As we guessed, the require_once method will not load the same file multiple times. But mixing it with require will make the require_once method invalid.
Copyright Statement: This article is an original article by the blogger and may not be reproduced without the blogger's permission.
The above introduces the use of php require_once and the difference with require, including the content. I hope it will be helpful to friends who are interested in PHP tutorials.

vue3+vite:src使用require动态导入图片报错和解决方法vue3+vite动态的导入多张图片vue3如果使用的是typescript开发,就会出现require引入图片报错,requireisnotdefined不能像使用vue2这样imgUrl:require(’…/assets/test.png’)导入,是因为typescript不支持require所以用import导入,下面介绍如何解决:使用awaitimport

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。


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