Number of posts written by a list of users.

Signature

count_many_users_posts( $users, $post_type = 'post', $public_only = false )
users
 (array) Array of user IDs.
post_type
 (string) Optional. Post type to check. Defaults to post.
Default: 'post'
public_only
 (boolean) Optional. Only return counts for public posts. Defaults to false.
Default: false

Return

(array) Amount of posts each user has written.

Source

function count_many_users_posts( $users, $post_type = 'post', $public_only = false ) {
	global $wpdb;

	$count = array();
	if ( empty( $users ) || ! is_array( $users ) )
		return $count;

	$userlist = implode( ',', array_map( 'absint', $users ) );
	$where = get_posts_by_author_sql( $post_type, true, null, $public_only );

	$result = $wpdb->get_results( "SELECT post_author, COUNT(*) FROM $wpdb->posts $where AND post_author IN ($userlist) GROUP BY post_author", ARRAY_N );
	foreach ( $result as $row ) {
		$count[ $row[0] ] = $row[1];
	}

	foreach ( $users as $id ) {
		if ( ! isset( $count[ $id ] ) )
			$count[ $id ] = 0;
	}

	return $count;
}
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