Getting the number of posts per category in Wordpress

This morning JTk presented me a WordPress riddle:

What I would like to be able to do is ask the MySQL if a category has any posts in it or if it is empty.  So I can do one thing if there are posts there and another if that category is empty.  And try as I might, no matter how hard I beat my head against it, all I get is a bruised head.  And, yes, I have to do this conditional because WP is flawed and will break if I try and do certain things with empty categories…..

Here is the schema ( maybe it helps )
http://blog.kapish.co.in/wp-content/uploads/2008/01/wp_db.png

And the worst part of this, is – I know this is trivial so I hate to even ask, but I guess I don’t hate enough not to ask  I asked the “community” and got told that there is not a WP function for this ( um, yeah, thanks…. ) that I shouldn’t make straight db calls ( arrrggg ), and that there are plugins that accomplish similar things….  But no real help, so I decided to ask a ninja….

So we want to get the number of posts per category. JTk, you’re in luck! A quick look at the schema (if that diagram is current) tells me we could query the wp_post2cat table and do a COUNT and a GROUP BY query on the category of interest. Even better, if wp_categories.category_count is what I think it is, that’s a simpler query. But let’s see what the code gives us already. In category.php, there are some tasty sounding functions like get_categories(), get_category(), get_category_by_path(), get_category_by_slug() and so on. I installed a clean version of WordPress, added some categories and assigned some fake posts to them. Then I tried some of these functions to see what’s up.

<?php var_dump(get_categories()); ?>

Output:

array(3) {
  [1]=>
  object(stdClass)#68 (15) {
    ["term_id"]=>
    &string(1) "3"
    ["name"]=>
    &string(14) "First Category"
    ["slug"]=>
    &string(14) "first-category"
    ["term_group"]=>
    string(1) "0"
    ["term_taxonomy_id"]=>
    string(1) "3"
    ["taxonomy"]=>
    string(8) "category"
    ["description"]=>
    &string(0) ""
    ["parent"]=>
    &string(1) "0"
    ["count"]=>
    &string(1) "4"
    ["cat_ID"]=>
    &string(1) "3"
    ["category_count"]=>
    &string(1) "4"
    ["category_description"]=>
    &string(0) ""
    ["cat_name"]=>
    &string(14) "First Category"
    ["category_nicename"]=>
    &string(14) "first-category"
    ["category_parent"]=>
    &string(1) "0"
  }
  [2]=>
  object(stdClass)#69 (15) {
    ["term_id"]=>
    &string(1) "4"
    ["name"]=>
    &string(15) "Second Category"
    ["slug"]=>
    &string(15) "second-category"
    ["term_group"]=>
    string(1) "0"
    ["term_taxonomy_id"]=>
    string(1) "4"
    ["taxonomy"]=>
    string(8) "category"
    ["description"]=>
    &string(0) ""
    ["parent"]=>
    &string(1) "0"
    ["count"]=>
    &string(1) "2"
    ["cat_ID"]=>
    &string(1) "4"
    ["category_count"]=>
    &string(1) "2"
    ["category_description"]=>
    &string(0) ""
    ["cat_name"]=>
    &string(15) "Second Category"
    ["category_nicename"]=>
    &string(15) "second-category"
    ["category_parent"]=>
    &string(1) "0"
  }
  [3]=>
  object(stdClass)#90 (15) {
    ["term_id"]=>
    &string(1) "1"
    ["name"]=>
    &string(13) "Uncategorized"
    ["slug"]=>
    &string(13) "uncategorized"
    ["term_group"]=>
    string(1) "0"
    ["term_taxonomy_id"]=>
    string(1) "1"
    ["taxonomy"]=>
    string(8) "category"
    ["description"]=>
    &string(0) ""
    ["parent"]=>
    &string(1) "0"
    ["count"]=>
    &string(1) "1"
    ["cat_ID"]=>
    &string(1) "1"
    ["category_count"]=>
    &string(1) "1"
    ["category_description"]=>
    &string(0) ""
    ["cat_name"]=>
    &string(13) "Uncategorized"
    ["category_nicename"]=>
    &string(13) "uncategorized"
    ["category_parent"]=>
    &string(1) "0"
  }
}

OK, so it sounds like the person who told JTk there were no built-in WordPress functions for this was lying   This function tells us exactly what we need. A couple of interesting observations, though. I had a category named “Empty Category” with no posts, which does not show up here. The documentation page tells me that I can pass a parameter to include the empty ones easily enough:

<?php var_dump(get_categories(array(‘hide_empty’=>false))); ?>

array(4) {
  [0]=>
  object(stdClass)#67 (15) {
    ["term_id"]=>
    &string(1) "5"
    ["name"]=>
    &string(14) "Empty Category"
    ["slug"]=>
    &string(14) "empty-category"
    ["term_group"]=>
    string(1) "0"
    ["term_taxonomy_id"]=>
    string(1) "5"
    ["taxonomy"]=>
    string(8) "category"
    ["description"]=>
    &string(0) ""
    ["parent"]=>
    &string(1) "0"
    ["count"]=>
    &string(1) "0"
    ["cat_ID"]=>
    &string(1) "5"
    ["category_count"]=>
    &string(1) "0"
    ["category_description"]=>
    &string(0) ""
    ["cat_name"]=>
    &string(14) "Empty Category"
    ["category_nicename"]=>
    &string(14) "empty-category"
    ["category_parent"]=>
    &string(1) "0"
  }
  [1]=>
  object(stdClass)#68 (15) {
    ["term_id"]=>
    &string(1) "3"
    ["name"]=>
    &string(14) "First Category"
    ["slug"]=>
    &string(14) "first-category"
    ["term_group"]=>
    string(1) "0"
    ["term_taxonomy_id"]=>
    string(1) "3"
    ["taxonomy"]=>
    string(8) "category"
    ["description"]=>
    &string(0) ""
    ["parent"]=>
    &string(1) "0"
    ["count"]=>
    &string(1) "4"
    ["cat_ID"]=>
    &string(1) "3"
    ["category_count"]=>
    &string(1) "4"
    ["category_description"]=>
    &string(0) ""
    ["cat_name"]=>
    &string(14) "First Category"
    ["category_nicename"]=>
    &string(14) "first-category"
    ["category_parent"]=>
    &string(1) "0"
  }
  [2]=>
  object(stdClass)#69 (15) {
    ["term_id"]=>
    &string(1) "4"
    ["name"]=>
    &string(15) "Second Category"
    ["slug"]=>
    &string(15) "second-category"
    ["term_group"]=>
    string(1) "0"
    ["term_taxonomy_id"]=>
    string(1) "4"
    ["taxonomy"]=>
    string(8) "category"
    ["description"]=>
    &string(0) ""
    ["parent"]=>
    &string(1) "0"
    ["count"]=>
    &string(1) "2"
    ["cat_ID"]=>
    &string(1) "4"
    ["category_count"]=>
    &string(1) "2"
    ["category_description"]=>
    &string(0) ""
    ["cat_name"]=>
    &string(15) "Second Category"
    ["category_nicename"]=>
    &string(15) "second-category"
    ["category_parent"]=>
    &string(1) "0"
  }
  [3]=>
  object(stdClass)#90 (15) {
    ["term_id"]=>
    &string(1) "1"
    ["name"]=>
    &string(13) "Uncategorized"
    ["slug"]=>
    &string(13) "uncategorized"
    ["term_group"]=>
    string(1) "0"
    ["term_taxonomy_id"]=>
    string(1) "1"
    ["taxonomy"]=>
    string(8) "category"
    ["description"]=>
    &string(0) ""
    ["parent"]=>
    &string(1) "0"
    ["count"]=>
    &string(1) "1"
    ["cat_ID"]=>
    &string(1) "1"
    ["category_count"]=>
    &string(1) "1"
    ["category_description"]=>
    &string(0) ""
    ["cat_name"]=>
    &string(13) "Uncategorized"
    ["category_nicename"]=>
    &string(13) "uncategorized"
    ["category_parent"]=>
    &string(1) "0"
  }
}

Sure enough,there is the empty category. I also noticed that the article count appears in both ->count and ->category_count. I’ll just assume the cached version, ->category_count, will remain correct through the code, but I’m just guessing it doesn’t matter which member we use.

So, that’s fine if we want the whole collection, but what about individual categories? Fortunately, we can extract this same data for both the category ID as well as the name of the category. Here’s an example of each, querying my “First Category” category:

Using ->category_count

<?php var_dump( (int) get_category(’3′)->category_count); ?>

<?php var_dump( (int) get_category_by_slug(‘First Category’)->category_count; ?>

<?php var_dump( (int) get_category_by_slug(‘first-category’)->category_count); ?>

Using ->count

<?php var_dump( (int) get_category(’3′)->count); ?>

<?php var_dump( (int) get_category_by_slug(‘First Category’)->count; ?>

<?php var_dump( (int) get_category_by_slug(‘first-category’)->count); ?>

All of these return the correct result, int(4). Good on ya, WordPress.

Now let’s see how robust the function is. Will it choke on a non-existent category, or return a zero like it should?

<?php var_dump( (int) get_category(’6969′)->category_count); ?>

<?php var_dump( (int) get_category_by_slug(‘This Damn Category’)->category_count); ?>

Both of these do indeed return zero, which is nice and correct.

In practical terms, you can use this code stub to do something will all categories depending on whether or not there are posts:

foreach (get_categories(array('hide_empty'=>false)) as $category){
	if ($category->count > 0){
		//has posts, do something
	}else{
		//no posts, do something else
	}
}

That’s all there is to it!  There’s definitely a built in function to inspect categories, and even some nice examples to go with. Happy WordPress hacking, and don’t forget that now’s the time to upgrade to PHP 5 if you haven’t already

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