What steps should be taken to troubleshoot and resolve the "Call to undefined function mysql_connect" error in PHP 5?

The "Call to undefined function mysql_connect" error occurs when the MySQL extension is not enabled in PHP 5. To resolve this issue, you need to enable the MySQL extension by editing the php.ini file and uncommenting the line extension=php_mysql.dll (Windows) or extension=mysql.so (Linux). Restart the web server after making the changes.

// Enable the MySQL extension in php.ini
// Uncomment the line below based on your operating system
// For Windows:
// extension=php_mysql.dll
// For Linux:
// extension=mysql.so