In what scenarios should the require_once and include_once statements be used in PHP programming to avoid errors related to function redeclaration?

When dealing with PHP scripts that include or require files containing functions, using require_once or include_once statements can prevent errors related to function redeclaration. These statements ensure that the file is included only once, even if it is referenced multiple times within the script. This is useful in scenarios where including the same file multiple times could lead to function redeclaration errors.

// Example of using require_once to include a file containing functions
require_once 'functions.php';

// Now you can safely call the functions without worrying about redeclaration
myFunction();