Почему php array_unique ($ array); производя повторяющиеся значения

У меня есть функция php, которую я пытаюсь сделать максимально эффективной, но есть избыточность, от которой я не могу избавиться. Поэтому мне нужна помощь.

Вот фактический код, если вы хотите посмотреть

function array_tags( $classes, $item, $args ){
if ( 'themes' === $args->theme_location ) {
$tagsString = "";
//cannot have spaces!!!!! change the page_title for something else
$cat = get_queried_object();
$catSlug = $cat->slug;

$args = array(
'post_type' => 'product',
'product_cat' => $catSlug,
'posts_per_page' => -1,
);
$loop = new WP_Query( $args );
if ( $loop->have_posts() ) {

while ( $loop->have_posts() ) : $loop->the_post();
global $product;

$tagsString .=  strip_tags($product->get_tags()) . ", ";
endwhile;
} else {

}
wp_reset_postdata();


$arr_tags = explode( ", ", $tagsString );

var_dump(array_unique($arr_tags));
if( !in_array($item->title, array_unique($arr_tags)) ){
$classes[] = "not-the-droid-you-are-looking-for";
}
else{

}
}
return $classes;
}
add_filter('nav_menu_css_class', 'array_tags', 10, 3);

вот вывод для var_dump($arr_tags);

array(12) {
[0]=> string(20) "Discover your Wonder"[1]=> string(3) "web"[2]=> string(6) "aliens"[3]=> string(9) "astrology"[4]=> string(16) "celestial bodies"[5]=> string(20) "Discover your Wonder"[6]=> string(5) "humor"[7]=> string(9) "mythology"[8]=> string(7) "science"[9]=> string(5) "space"[10]=> string(20) "Discover your Wonder"[11]=> string(0) ""}
array(12) {
[0]=> string(20) "Discover your Wonder"[1]=> string(3) "web"[2]=> string(6) "aliens"[3]=> string(9) "astrology"[4]=> string(16) "celestial bodies"[5]=> string(20) "Discover your Wonder"[6]=> string(5) "humor"[7]=> string(9) "mythology"[8]=> string(7) "science"[9]=> string(5) "space"

и так далее, почему var_dump в $ arr_tags создает несколько массивов?

также здесь var_dump($tagsString)

string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, "

вот вывод var_dump(strip_tags($product->get_tags()));

string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, "

вот вывод var_dump((string)strip_tags($product->get_tags()));

string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, " string(25) "Discover your Wonder, web" string(91) "aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space" string(20) "Discover your Wonder" string(142) "Discover your Wonder, web, aliens, astrology, celestial bodies, Discover your Wonder, humor, mythology, science, space, Discover your Wonder, "