Why Am I Getting the 'Fatal Error: Call to Undefined Function mysqli_connect()' in PHP?

Resolving "Fatal Error: Call to Undefined Function mysqli_connect()"

Problem Description:

A user encounters the error "Fatal error: Call to undefined function mysqli_connect()" when attempting to establish a connection to a MySQL database using PHP. The code responsible for connecting to the database appears to be correct and has been tested successfully on localhost and the previous server.

Solution:

The error indicates that the PHP extension for MySQL, "mysqli," is not installed or enabled. To resolve this issue, follow these steps:

1. Install the mysqli Extension:

   Ubuntu/Debian:

   sudo apt install php-mysqli

   CentOS/Red Hat:

   yum install php-mysqli

2. Restart Apache or Nginx:

   Restart your web server to activate the newly installed or enabled extension.

   Apache:

   sudo systemctl restart apache2

   Nginx:

   sudo systemctl restart nginx

3. Verify Installation:

   Ensure that the extension has been successfully installed by creating a new PHP file and adding the following code:

   <?php
   if (function_exists('mysqli_connect')) {
       echo "mysqli_connect function is available";
   } else {
       echo "mysqli_connect function is not available";
   }
   ?>

   Run the PHP file to verify the availability of the mysqli_connect function. It should display "mysqli_connect function is available".

By installing and enabling the mysqli extension, the user can establish a connection to the MySQL database and resolve the "Fatal error: Call to undefined function mysqli_connect()" error.

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