I have an $array that prints out to be as follows.

Array ( [post-12] => 12 [post-160] => 160 )

What WordPress function could I use to check how many of the post ID's in the array belong to a specific category, say category with ID 45.

I tried doing the following.

$post_id_array = $array;
$category = '45';
$count = count(in_category( $category, $post_id_array ));
echo $count;

It doesn't work.

  • OK, can some mod transfer this question there?
    – Sam
    Dec 28, 2014 at 9:57
  • You can try to flag it for moderator attention with the explicit reason, but I'm not 100% sure they can do that. Or you can copy/paste and delete this one ;-)
    – TLama
    Dec 28, 2014 at 9:58

2 Answers 2


A much faster solution would be to query the database once instead of over and over for each post ex:

function count_posts_in_term($posts = array(),$term_taxonomy_id = 0){
    global $wpdb;
    $count = 0 ;
    $count = $wpdb->get_var(
        $wpdb->prepare("SELECT count(object_id) 
            FROM $wpdb->term_relationships 
            WHERE term_taxonomy_id = %s 
            AND object_id IN(".implode(',',$posts).")",
    return $count;


echo count_posts_in_term($array_of_posts,$cat_term_id);

I have successfully returned the counts using the following code. Just in case someone may later view this question.

$count = 0;
$category = '45';
foreach ( $array as $post_id ) {
    if (in_category( $category, $post_id )) {
echo $count;

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