Let's talk about the writing of reference paths in PHP development

With the development of the Internet, various programming languages ​​have increasingly become one of the necessary skills for developing websites and applications. Among them, PHP, as a more mainstream programming language, is widely used in many fields. Regarding the writing of reference paths in PHP development, let's discuss the relevant knowledge.

Overview of Reference Paths

When writing PHP programs, we often need to introduce code snippets from other files, and also need to reference external resource files, such as style sheets, JavaScript files, and images. In order to ensure that these external resources can be referenced and loaded correctly, we need to use paths to specify their locations.

Classification of reference paths

In PHP, paths can be divided into two types: relative paths and absolute paths.

Relative path

The relative path refers to the relative position relationship between the current file and the referenced file. Relative paths are divided into the following two types.

1. The path relative to the current file

The path relative to the current file refers to the situation where the reference file and the current file are in the same directory. In this case, just use the file name in the referenced file. For example, to reference the file.php file in the current directory, you can use the following code to reference:

include('file.php');

2. relative to the parent directory path of the current file

relative to The parent directory path of the current file refers to the situation where the reference file and the current file are in different directory levels. At this time, you need to specify a relative path based on the hierarchical relationship between the reference file and the current file. For example, assuming that the current file is /example/dir1/file1.php, and to reference the upper-level directory /example/dir2/dir3/file2.php, you can use the following code to reference:

include('../../dir2/dir3/file2.php');

Absolute path

The absolute path is the path starting from the server root directory. When using an absolute path, you need to add / (slash) before the path to indicate starting from the root directory. For example, to reference the config.php file in the root directory of the website, you can use the following code to reference:

include('/config.php');

Note: When using absolute paths, you need to pay attention to the file path structure of the server to ensure the correctness of the path.

Reference path example

Take a typical PHP reference path example:

1. Assume that a file needs to be referenced in the PHP program, and the file name is file.php , the file is stored in the subdirectory sub of the directory where the current file is located.

/
|- index.php
|- sub
   |- file.php

In index.php, you need to reference the file.php file in the sub directory. You can use relative paths for reference.

include('sub/file.php');

2. Assume that an external stylesheet needs to be referenced in the PHP program. The file name is style.css and the file is stored in the root directory of the website.

/
|- index.php
|- style.css

In index.php, you need to reference the style.css style sheet file in the root directory of the website. You can use the absolute path for reference.

<link rel="stylesheet" href="/style.css">

3. Assume that an external JavaScript file needs to be referenced in the PHP program. The file name is script.js. The file is stored in the parent directory of the directory where the current file is located.

/
|- index.php
|- public
   |- script.js

In index.php, you need to reference the script.js file one level above the public directory (that is, the parent directory of the current directory). You can use relative paths for reference.

<script src="../public/script.js"></script>

Summary

Reference path is a very important basic knowledge point in PHP programming. Proper use of different types of paths can make program development and resource reference more convenient and accurate. In the actual development process, relative paths or absolute paths need to be used according to specific circumstances, and great attention must be paid to the correctness of the paths to ensure the normal operation of the program.

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