Incomplete term slugs output from a foreach loop with get_the_terms

Question

I'm using this PHP to get all the product category slugs on a single product page:

global $post;
$terms = get_the_terms( $post->ID, 'product_cat' );
if(is_array($terms)){
foreach ($terms as $term) {
    $product_cat_slug = $term->slug;
    $product_cat_slugs = ' product_cat-' . $product_cat_slug;
    echo $product_cat_slugs;
}
}

The line echo $product_cat_slugs; outputs product_cat-category1 product_cat-category2, which I will use for div classes.

The problem is that when I delete the echo $product_cat_slugs; from the function above and use <?php echo $product_cat_slugs; ?> elsewhere on the page, all I get for output is the last category slug product_cat-category2, and not both categories product_cat-category1 product_cat-category2.

What's wrong? It appears that $product_cat_slugs is overwritten when outside the foreach; how can I prevent that?

Answer 1

You are overwriting $product_cat_slugs on every iteration of your loop - so when it's finished, that variable will be set to the last value.

Why not do all of your outputs inside that loop?

Or if for some reason you don't want to do that, make $product_cat_slugs an array instead of a variable:

$product_cat_slugs = [];
foreach ($terms as $term) {
    $product_cat_slug = $term->slug;
    $product_cat_slugs[] = ' product_cat-' . $product_cat_slug;
}