What is file mode in php file operations? How to change file mode?

In the PHP development process, there are many situations where files need to be operated (such as file uploads, etc.), so file directory operations play an important role. Starting from this article, we will talk about file operations in PHP through a series of articles, from simple to difficult, let's start learning with me. (I am still a newbie exploring the PHP road a little bit. Let’s watch "PHP Video Tutorial" to learn PHP. Everything you want is here!)

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As mentioned in the title, the center of this article is to talk about file mode. First, let’s take a brief look at the file mode in PHP.

Before operating a file, our first step is to open the file; when opening the file, we need to consider how to use it? What do you want to do with the open file? That is, in what mode is it opened (read-only? write-only? or read-write mode?).

File mode can specify: after a file is opened, whether other scripts are allowed to open it again, and whether the user (or script) has the permission to use the file in this way.

When writing a file, there are several situations: one is to clear the original content of the file and write new data (that is, overwrite all existing file contents); one is to directly append new data to End of file; the other is to insert new data at the beginning of the file.

Okay, above we have a brief understanding of the file mode in PHP, let's take a look at How does PHP change the file mode?

In PHP, we can change the file mode through the built-in function chmod(). This function can change the permissions of the specified file and change the mode of the specified file to the user. Specified specific mode.

chmod() function can accept two parameters: $filename and $mode; among them, $filename specifies the need to change Permissions file, $mode is used to specify new permissions.

$modeThe parameter consists of four values, the first value is always zero, the second value specifies the owner's permissions, and the third value specifies the owner's user group permissions, and the fourth value specifies permissions for everyone else.

The number representing permissions has three possible values. To set multiple permissions, you can use the following numbers for totaling:

• 1 = Execute permissions

• 2 = Write permission

• 4 = Read permission

Example:

• 5 = 4 1 = Read execute permission

• 6 = 4 2 = Read write permission

• ##7 = 4 2 1 = Read, write and execute permissions, that is, provide all permissions

Let’s use code examples to learn more about how PHP’s built-in function chmod() changes the file mode. .

Example 1:Set the owner to have read and write permissions, and others cannot

<?php
chmod("PHP.txt", 0600);
?>

It can be seen:

$modeThe parameter is "0600", only the owner's permission is set to 6 (read and write).

Output:

TRUE

Description: When using the chmod() function to change the file mode, TRUE is returned if successful, and FALSE if failed.

Example 2:Set the owner to have read and write permissions, and everyone else only has read permissions

<?php
chmod("PHP.txt", 0644);
?>

Output:

TRUE

## The #$mode

parameter is "0644", then the owner's permissions are 6 (read-write), and the owner's user group and everyone else's permissions are 4 (read-only).

Example 3:

Set all permissions for the owner, and everyone else has read and execute permissions

<?php
chmod("PHP.txt", 0755);
?>

Output:

TRUE

$mode

The parameter is "0755", then the owner's permissions are 7 (read, write and execute permissions), and the permissions of the owner's user group and everyone else are 5 (read and execute permissions). Okay, that’s all. If you want to know anything else, you can click this. → →

PHP file basic operations

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