Where can one find resources or documentation to help troubleshoot undefined constant errors in PHP scripts?

Undefined constant errors in PHP scripts occur when a constant is used without being defined first. To troubleshoot this issue, check if the constant is defined using the defined() function or ensure that the constant is properly defined with the define() function before using it in the script.

if (!defined('MY_CONSTANT')) {
    define('MY_CONSTANT', 'my_value');
}