Question

A WordPress function should return the top level term id of a given child term id – terms can have 1..n parents, so a recursive function seems to be useful here.

// Recursive function
function return_top_level_term($term_id, $taxonomy_name) {
    $term = get_term_by('id', $term_id, $taxonomy_name);
    if($term->parent>0) {
        return_top_level_term($term->parent, $taxonomy_name);
    } else {
            // Here we get the correct value
        return $term->term_id;
    }
}

PHP indeed does find the correct term_id, but the function always returns false.

$my_top_level_term = return_top_level_function(423, $tax);

Example with three layers, informal notation:

return_top_level_term(return_top_level_term(return_top_level_term(return 1;)return false;) return false;)

I am searching for the 1, but false is always returned, although the the function does not have a return value.

Of course I could write a local variable above the function which can save the value because of the scope rules, but I want to write it into a library – is there a way of returning this value by calling the recursive function?

Answer 1

Change this line

return_top_level_term($term->parent, $taxonomy_name);

to

return return_top_level_term($term->parent, $taxonomy_name);

Otherwise, the last result will not be returned to the top function on the stack and the return will be void.