Detailed explanation on the usage of set_include_path() function in PHP

This article mainly introduces the usage of the set_include_path() function in PHP, and analyzes the related skills of PHP for file path setting in the form of examples. It has certain reference value. Friends in need can refer to it

First look at the following code:

<?php
/** 定义根目录 */
define(&#39;__TYPECHO_ROOT_DIR__&#39;, dirname(__FILE__));
/** 定义插件目录(相对路径) */
define(&#39;__TYPECHO_PLUGIN_DIR__&#39;, &#39;/usr/plugins&#39;);
/** 设置包含路径 */
@set_include_path(get_include_path() . PATH_SEPARATOR .
__TYPECHO_ROOT_DIR__ . &#39;/var&#39; . PATH_SEPARATOR .
__TYPECHO_ROOT_DIR__ . __TYPECHO_PLUGIN_DIR__);
?>

First:

Let’s look at this global variable: __FILE__

it Indicates the full path of the file (including the file name of course)

That is to say, it has different values ​​depending on the directory where your file is located; of course, when it is used in a package line file, it The value is the included path;

Then:

We look at this function:

string dirname ( string path )

It is a PHP built-in function , what is its function, is to return the directory other than the file name, for example:

If you use the _FILE_ variable in your homepage:

(assuming your The directory where the web page is located is: http://localhost/web/index.php), then: the value of
_FILE_ is http://localhost/web/index.php (an absolute path). At this time, dirname (_FILE_) represents http://localhost/web/, which means there is no file name index.php.

And dirname(dirname(_FILE_)) represents the upper-level directory, and so on;

Finally:

Look at the define() function, in fact It is a function that defines constants, such as: define('MEN','ooooo');

Then you can use MEN to represent the string ooooo;

That's it What's the advantage of writing is that when you need to modify a variable, you just need to modify it, which is quite convenient, especially for strings like paths!

Let’s explain this code:

define('__TYPECHO_ROOT_DIR__', dirname(__FILE__));

is to define __TYPECHO_ROOT_DIR__ as the directory where this file is located. A definition like this is usually If placed in config.inc.php, then the directory obtained is the directory where config.inc.php is located; that is, the root directory!

define('__TYPECHO_PLUGIN_DIR__', '/usr/plugins');

It goes without saying!

As for what set_include_path(get_include_path() . PATH_SEPARATOR . $path); means, it is the include path;

For example, if you have a folder: named include, there is a database connection file in it :conn.php......,

You set it like this:

set_include_path("/include")

Then you can use it directly in other pages in the future

include("conn.php")

Isn’t this often seen? Its parameters are strings. Of course, you can also set multiple paths, separated by ;. What does that sentence:

set_include_path(get_include_path() . PATH_SEPARATOR .
__TYPECHO_ROOT_DIR__ . '/var' . PATH_SEPARATOR .
__TYPECHO_ROOT_DIR__ . __TYPECHO_PLUGIN_DIR__);

mean? For example :

One of your pages has this statement:

include('/inc/sql.php');
include('/inc/conn.php');

And you suddenly discovered that I put these files to be included in the inc directory It’s not safe to download. What should I do? I want to change it. I want to put it in the include directory. Okay, it’s weird if I don’t get exhausted with so many pages: Is there a good way? have! ! ! ! ! ! !

Write this sentence in config.inc.php:

set_include_path(get_include_path() .'/include')

It’s that simple, yes, it’s that simple! Dynamic modification!

Don’t look at this: get_include_path() . PATH_SEPARATOR . $path What is this? It is just a path string. The middle one is the string connection symbol, which is a combination of the constants just defined. Into a string, which means he can dynamically set the include path! If the included path is returned correctly, false is returned incorrectly;

Summary: The above is the entire content of this article, I hope it will be helpful to everyone's learning.

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