get_cat_ID() not wokring

Question

I'm writing a function in functions.php. I am working with woocommerce and trying to get posts with the same cat name of product_cat on single product pages. My idea is using the cat name of woocommerce cat and get_cat_ID() to get the category ID, then use WP_query to get the posts. However, get_cat_ID() always returns 0 (I event create a category called 'test', but still). Tried to google the problem but no solution. get_cat_ID() seems to be really straightforward so I am really not sure what went wrong. It would be great if anyone can let me know what would be the possible reason.

To sum up my problem: I have a product_cat named 'test'. Now I want to get the ID of the category with the same name 'test'.

Here's the code:

$cate_object = get_the_terms( $post->ID, 'product_cat' );
foreach( $cate_object as $cate ){
    // get cat id by tax name
    $thisCatName = $cate->name;
    $thisCatID = get_cat_ID($thisCatName);
    if($thisCat !== null && $thisCat != 0)
        $cat_array[] = $thisCatID;
}

Thanks!

Answer 1

get_cat_ID gets the ID of a category based on the name. "Category" is a specific taxonomy named category. You're trying to get the ID of a Product Category (product_cat). You cannot use get_cat_ID() to get the ID of a custom taxonomy.

To do that you need to use get_term_by():

$product_cat = get_term_by( 'name', $cat_name, 'product_cat' );

if ( $product_cat ) {
    $thisCatID = $product_cat->term_id;
}

But, based on your code, you don't need to be finding the ID. You already have it:

$cate_object = get_the_terms( $post->ID, 'product_cat' );
foreach( $cate_object as $cate ){
    $thisCatID = $cate->term_id; // This is the ID.

    $cat_array[] = $thisCatID;
}

Answer 2

For people who has the same problem: I think the problem is caused by Polylang. I checked my category list on dashboard, and realized that the category I failed to get with get_cat_ID() doesn't belong to any language (which is weird). I created a test category and give assign a language to it, then get_cat_ID() works!

Thanks to people who tried to help out!