What should I do if the relative directory in php cannot be opened?

Solution to the problem that php cannot be opened in a relative directory: 1. Use "absolute path"; 2. Define a general function import.php, set it to "automatically import files in advance", and add it in php.ini Just modify the content to "auto_prepend_file = "C:\xampp\htdocs\auto_prepend_file.php"".

The operating environment of this tutorial: Windows 7 system, PHP version 8.1, Dell G3 computer.

php Relative directory cannot be opened? Summary of require and include path issues in PHP

1 Absolute path, relative path and undetermined path

Relative path

Relative path refers to the path starting with., For example

./a/a.php (相对当前目录)    
../common.inc.php (相对上级目录)，

Absolute path

The absolute path is a path starting with / or a drive letter similar to C:/ under Windows. The full path can uniquely determine the final file without any reference path. address. For example

/apache/wwwroot/site/a/a.php
c:/wwwroot/site/a/a.php

Undetermined path

Any path that does not start with . or /, nor does it start with the Windows drive letter:/, for example

a/a.php  
common.inc.php，

I initially thought this was also a relative path Path, but in PHP's include/require inclusion mechanism, this type of path is completely different from the relative path processing starting with . require './a.php' and require 'a.php' are different!

Let’s analyze the processing methods of these three types of include paths: First, remember a conclusion: if the include path is a relative path or an absolute path, it will not go to include_path (include_path defined in php.ini Environment variables, or use set_include_path(...) in the program to find the file.

Test environment description

Note: The following discussion and conclusion are based on this environment: Assumption A=http://www.xxx.com/app/test/ a.php, again emphasize that the following discussion is for the case of direct access to A.

2. Relative path:

The relative path requires a reference directory to determine the final path of the file. In the include resolution, No matter how many levels of nesting are included, this reference directory is the directory where the program execution entry file is located .

Example 1

A中定义  require './b/b.php';  // 则B=[SITE]/app/test/b/b.php
B中定义  require './c.php';    // 则C=[SITE]/app/test/c.php 不是[SITE]/app/test/b/c.php

Example 2

A中定义  require './b/b.php';  // 则B=[SITE]/app/test/b/b.php 
B中定义  require '../c.php';   // 则C=[SITE]/app/c.php  不是 [SITE]/app/test/c.php

Example 3

A中定义  require '../b.php';   //则B=[SITE]/app/b.php 
B中定义  require '../c.php';   //则C=[SITE]/app/c.php  不是 [SITE]/c.php

Example 4:

A中定义  require '../b.php';   // 则B=[SITE]/app/b.php 
B中定义  require './c/c.php';  / /则C=[SITE]/app/test/c/c.php  不是 [SITE]/app/c/c.php

Example 5

A中定义  require '../inc/b.php';  // 则B=[SITE]/app/inc/b.php 
B中定义  require './c/c.php';     // 则C还是=[SITE]/app/test/c/c.php  不是 [SITE]/app/inc/c/c.php

Example 6

A中定义  require '../inc/b.php';  // 则B=[SITE]/app/inc/b.php 
B中定义  require './c.php';       // 则C=[SITE]/app/test/c.php  不是 [SITE]/app/inc/c.php

3. Absolute path

The absolute path is relatively simple and not easy to cause confusion and errors. require|inclue corresponds to the file on the disk.

require '/wwwroot/xxx.com/app/test/b.php';    // Linux中
require 'c:/wwwroot/xxx.com/app/test/b.php';  // windows中

dirname(__FILE__) is also calculated as a directory in the form of an absolute path, but it should be noted that __FILE__ is a Magic constants, and it is equivalent to writing this statement at any time. The absolute path where the php file is located, so dirname(__FILE__) always points to the absolute path of the php file where this statement is written, and has nothing to do with whether this file is included and used by other files.

Example 1

A中定义  require '../b.php';                  // 则B=[SITE]/app/b.php
B中定义  require dirname(__FILE__).'/c.php';  // 则B=[SITE]/app/c.php

Example 2

A中定义  require '../inc/b.php';              // 则B=[SITE]/app/inc/b.php
B中定义  require dirname(__FILE__).'/c.php';  // 则B=[SITE]/app/inc/c.php 始终跟B在同一个目录

Conclusion: No matter whether B is included and used by A, or directly accessed

B如果 require dirname(__FILE__).'/c.php';    // 则始终引用到跟B在同一个目录中的 c.php文件; 
B如果 require dirname(__FILE__).'/../c.php'; // 则始终引用到B文件所在目录的父目录中的 c.php文件; 
B如果 require dirname(__FILE__).'/c/c.php';  // 则始终引用到B文件所在目录的c子目录中的 c.php文件;

4. Undetermined path

First use the include directories defined in include_path to splice [undetermined path] one by one. If an existing file is found, the include will exit successfully. If not found, use the directory where the php file that executes the require statement is located to splice [ Undetermined path] to find the file. If the file exists, it will exit successfully. Otherwise, it means the file does not exist and an error will occur. Undetermined paths are easy to confuse and are not recommended.

5. Solution

Since the "reference directory" in the "relative path" is the directory where the execution entry file is located, "undetermined" The path is also easy to confuse, so the best solution is to use the "absolute path" ; For example, the content of b.php is as follows, no matter where b.php is required, the path of b.php will be used as a reference Come to require

$dir = dirname(__FILE__);
require($dir . '../c.php');

of c.php or define a general function import.php, set it to "automatically import files in advance", and make the following configuration in php.ini

更改配置项（必须）auto_prepend_file = "C:\xampp\htdocs\auto_prepend_file.php"
更改配置项（可选）allow_url_include = On

import.php The content is as follows

function import($path) {    
    $old_dir = getcwd();        // 保存原“参照目录”
    chdir(dirname(__FILE__));    // 将“参照目录”更改为当前脚本的绝对路径
    require_once($path);
    chdir($old_dir);            // 改回原“参照目录”
}

In this way, you can use the import() function to require the file. No matter how many levels of "reference directories" it contains, it is the current file

Recommended learning: "PHP Video Tutorial 》

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