How can PHP developers troubleshoot and debug errors related to language constants being redefined in their code?

When PHP developers encounter errors related to language constants being redefined in their code, they can troubleshoot and debug by checking for duplicate constant declarations and ensuring that constants are defined only once throughout the codebase. To avoid redefining constants, developers can use the `defined()` function to check if a constant is already defined before declaring it.

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