Discuss the reasons and solutions for functions that cannot be used in php.ini

In PHP development, the php.ini file is one of the essential configuration files, which stores various configuration information of the PHP parser. Whether deploying in a local development environment or on a server, we often need to modify the php.ini file to meet our needs.

However, we may encounter a very difficult problem - some PHP functions are disabled. We find the corresponding configuration in php.ini and find that the configuration is already enabled. Why can't I still use these functions? How to solve this problem?

This article will explore the reasons and solutions for functions that cannot be used in php.ini.

1. Problem Analysis

First of all, it needs to be clear that functions in PHP can be divided into two categories: built-in functions and extension functions. Built-in functions refer to functions that come with PHP, while extension functions are functions that can only be used after installing the corresponding extension library.

In the php.ini file, we also need to configure two types of functions separately. Next, we will take disabling built-in functions as an example to explain the specific reasons and solutions for why functions cannot be used.

1. View error message

When we use a disabled function, the error message usually displays "Fatal error: Call to undefined function XXX()".

At this time, we need to find the disable_functions configuration item in php.ini. If the value of this configuration item is empty, then the reason for disabling the built-in function is not a problem with the configuration file, but a problem with our environment or installation.

2. Restart the environment or service

If disable_functions is still empty, but we still cannot use the disabled function, it may be because the configuration file was not restarted after modification. The server or environment used.

The mainstream PHP development and production environments are:

• Apache
• Nginx
• PHP-FPM
• PHP built-in server

If we use PHP in Apache or Nginx, we need to restart the corresponding server.

If we are using PHP-FPM, we also need to restart the php-fpm service. The restart command is:

/sbin/service php-fpm restart

If we use the PHP built-in server, we need to use Ctrl C to end the current run and then restart the server.

3. Disable safe mode

Due to historical reasons, early versions of PHP introduced a safe mode, safe_mode, which is used to restrict program access to files, databases, etc. permissions. In safe mode, some commonly used functions may be disabled.

If our application does not need to use safe mode, we can modify the safe_mode configuration item in the php.ini file to off, and then restart the server or environment.

4. Disable Suhosin extension

Suhosin is a PHP extension whose purpose is to enhance the security of PHP. But in some cases, Suhosin disables some commonly used functions. If the Suhosin extension is installed on our server or environment, it can be disabled in php.ini.

Note: The Suhosin extension is not a PHP standard extension, so it needs to be installed manually.

5. Check server running permissions

In some high-security scenarios, we may need to fine-grained control of PHP running permissions. At this time, we need to check whether the permissions of the server running are correct. Specifically, we can check the user group of the PHP running user, file ownership and other information.

If our application needs to perform write operations on a certain directory or file, we need to ensure that the owner and group of the directory or file are in the user group of the user running PHP.

Summary

This article introduces the following aspects: checking the error message, rebooting the enironment, disabling safe mode, disabling Suhosin extension and checking permission of the server. Reasons and solutions for using functions.

To better solve the problem of the php.ini file being unable to use functions, we need to have an in-depth understanding of how to use a single PHP function, find all disabled functions, check the memory limit when the script is executed, and other issues. These are knowledge points that must be mastered in the PHP development process. Only with an in-depth understanding can we better solve the problems encountered.

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