Developing software and web applications in PHP can sometimes encounter various errors that hinder the proper functioning of the application. One such error is "Fatal error: Uncaught Error: Call to undefined function mb_convert_encoding()". This article provides a detailed guide on how to resolve this issue and prevent its recurrence.

Identifying the Problem

The "Fatal error: Uncaught Error: Call to undefined function mb_convert_encoding()" error occurs in PHP scripts when the mb_convert_encoding() function is called without the Multibyte String (mbstring) extension being installed and activated. The mbstring extension provides functionality for working with multibyte strings, which is essential for proper Unicode support in your applications.

Step 1: Verifying the Installation of the mbstring Extension

The first step is to check if the mbstring extension is installed on your server. This can be done in several ways:

• Creating a phpinfo.php File: Create a PHP file with the following code and place it on your web server:

<?php
phpinfo();
?>

After creating this file, open it in a web browser. Using the browser's search function, look for "mbstring". If you find the mbstring configuration, it means the extension is installed.

• Using the Command Line: If you have access to the server's command line, you can check the installation of mbstring using the php -m command, which will output all PHP extensions. If you see "mbstring" in the list, the extension is installed.

Step 2: Installing or Activating the mbstring Extension

If you have found that the mbstring extension is not installed, you will need to install or activate it.

• On Debian/Ubuntu:

  • You can install the mbstring extension using the command: sudo apt-get install php-mbstring
  • After installation, restart the web server, for example, Apache, using the command: sudo service apache2 restart

• On CentOS/RHEL:

  • Install it using: sudo yum install php-mbstring
  • After installation, restart the web server, for example: sudo systemctl restart httpd

• If using XAMPP or a similar local server:

  • Open the php.ini configuration file and search for the line ;extension=mbstring.
  • Remove the semicolon at the beginning of the line to uncomment and activate the extension.
  • Restart XAMPP or the PHP service.

Step 3: Testing Functionality

After installing or activating the mbstring extension, test its functionality. This can be done by creating a simple PHP script that uses the mb_convert_encoding() function and running this script in a web browser.

<?php
$text = "Příliš žluťoučký kůň";
$convertedText = mb_convert_encoding($text, "UTF-8");
echo $convertedText;
?>

If the script returns the expected output without errors, the mbstring extension is correctly installed and activated.

 

The solution for the "Fatal error: Uncaught Error: Call to undefined function mb_convert_encoding()" error in PHP involves verifying, installing, or activating the mbstring extension. This article provides a detailed procedure to resolve this issue and ensure that your PHP applications can smoothly work with multibyte strings.