What is the significance of the error message related to passing locale category name as a string in PHP?

When passing the locale category name as a string in PHP, it will result in an error because the function expects an integer constant instead. To solve this issue, you need to use the predefined constants for the locale category names instead of passing them as strings.

// Incorrect way of passing locale category name as a string
setlocale("LC_ALL", "en_US.UTF-8");

// Correct way of passing locale category name using predefined constants
setlocale(LC_ALL, "en_US.UTF-8");