Recursive function does not return array [duplicate] - php

Question

This question already has answers here:
How to use return inside a recursive function in PHP
(4 answers)
Closed 9 months ago.
I have written the function below to return parent id's of all categories in Worpress by category id. Everything works fine except it does not return the array... Any suggestions would be great! :-)
$current_category = (int) $_GET['current_category'];
$cat_ids = array($current_category);
function getParentCatIds($current_category,$cat_ids){
$child = get_category($current_category);
$parent_id = $child->parent;
if($parent_id !== 0){
array_push($cat_ids, $parent_id);
getParentCatIds($parent_id,$cat_ids);
}else{
var_dump($cat_ids); // <--- this returns the right array
return $cat_ids; // <--- this returns NULL
}
}
if($current_category){
$cat_ids = getParentCatIds($current_category,$cat_ids);
var_dump($cat_ids); // <--- this returns NULL
}

Answer 1

When you call getParentCatIds() (line 9), you didn't do anything with the return of the function. You should assign it or return it.

Answer 2

You should always sanitize input. A good starting point is filter_var(). Using the right flags for validation and sanitization and makes your input save(r). Keep in mind that FILTER_VALIDATE_* only tells you if something is valid, while FILTER_SANITIZE_* actually cleans your data from unwanted and potentially malicious data.
$currentCat = intval( $_GET['current_category'] );
$currentCat = filter_var( $currentCat, FILTER_SANITIZE_NUMBER_INT );
if ( empty( $currentCat ) ) {
// Abort – no valid data
return;
}
Then you can build an array, containing your original Category parent ID. This you can pass to array_walk(), with a callback as second parameter. The callback itself has assigned a collecting/ final array that is passed as reference and serves as target for your results. Now you can loop recursively over an indefineatly nested WordPress category hierarchy.
// Base array
$parents = [];
$callback = function( $index, $id ) use ( &$parent ) {
0 !== get_category( $id )->parent and $parents[] = $id;
};
array_walk( [ get_category( $currentCat )->parent ], $callback );

Answer 3

1) You should have asked at wordpress.stackexchange.com
2) I think solution is: on line 9 , instead of
getParentCatIds($parent_id,$cat_ids);
you should have
return getParentCatIds($parent_id,$cat_ids);