So you want to display a random list of posts, maybe in a sidebar widget…

One way to do it is to use the query_posts() function

<?php
    query_posts('showposts=6&amp;amp;orderby=rand'); 

    if (have_posts(){
	while (have_posts()){
	the_post();

	//do something with the postdata
	}
}
?>

But it’s easy to get in a mess with query_posts – as they do say…

The query_posts function overrides and replaces the main query for the page. To save your sanity, do not use it for any other purpose.

Often best to instantiate a new, completely separate object where you can see it, as it were:

	$args = array('showposts'=>6, 'orderby'=>'rand');
	$customQuery = new WP_Query($args);

	if($customQuery->have_posts()){
		while ($customQuery->have_posts()){
			$customQuery->the_post();
	//do something with the postdata
 }

}

It’s a good general rule to get into the practice of using WP_Query in cases like these – a lot safer…

Note, we’re talking here about different category archive pages – not having a post page customised according to the category that post is in….

There’s 2 ways of doing this – first, the simple way, for more minor changes to the overall theme template, you can use the is_category function:

if (is_category('featured')) {
// some different code here for the featured category archive
// such as, if this code is in the header, load a different or supplementary stylesheet
} else {
//code here for every other category - if required...
}

So for example, you could have a category set aside for video posts and have its archive page display extra information about each post, using get_post_meta()…
And single_cat_title() has its uses in this context.

Custom Category Templates

But secondly, just like WordPress page templates, you can customise by category by using a separate template file.

All you need to do is copy say, category.php to a new file: category-video.php and make the desired changes. This way, WordPress will find and load this file for you, via its priority in the template hierarchy

The template hierarchy: WordPress works down the list, checking for a match – the first file found that satisfies the criteria is the one used to display the archives for that category.

1st. category-slug.php – define category using its slug name (WP 2.9+ only)
2nd. category-ID.php – define category using its ID
3rd. category.php
4th. archive.php
5th. index.php – the default template

(Note also, it’s a hypen not an underscore)

This does amount to roughly the same thing as a conditional php include, but can be a more elegant way of doing things…

Sorry, but we don’t guarantee that our themes, free or premium, will work 100% if used in a WordPress multi-user environment.

Why not? Simply because there’s too great a variation in paths, subdomains and subfolders etc. and it just doesn’t seem to be possible to cover all eventualities – at present, anyway. This isn’t particularly the fault of the WordPress multi-user developers – it’s more about how Apache, mod_rewrite and the whims of hosting sysadmins fit together at the moment.

Themes can be made to work – on an individual basis, depending on your installation. But a lot of this will involve editing of paths in the theme functions.php, both for wp-content/ with things like loaded jQuery scripts and also wp-includes/ for including basic scripts, such as jQuery itself, permalinks and even images.

Also, not everyone has access to their server’s http.conf – and there are a number of tricks here, mainly involving AllowOverride, that can be used to get results with multi-user. It’s no good saying do this, and our themes will definitely work, if you can’t get at the actual file…

You might get lucky, if there’s luck in programming, and it will work straight out of the box – but, as I say, no guarantee.

1. Conditional functions

To begin at the beginning, we’re talking about is_home(), is_search() etc. The whole collection of functions is here – and the majority are handled in a very similar way.

This family of conditional functions is related to the template file hierarchy – and since their use can save a lot of time and duplication of code, it’s definitely worth learning how to manipulate them efficiently.

Template Hierarchy

Depending on the initial query, WordPress ‘decides’ which type of page, an archive page, a search page, a page page, is being requested – it then searches whether there’s a specific template file in the theme directory corresponding to this request – ie search.php, archive.php, page.php.

If there is, well and good – if there isn’t, it tries the next file down in the hierarchy, and if none fit the bill, it serves up the default, index.php.

And this is where one very common use of conditional functions comes in -
Using is_search() in index.php comes to much the same thing as using a search.php file. If you’re planning only a few variations in code this is the way to go.

So, here’s an example of a control structure in index.php, testing whether the requested page is a search page, with is_search() returning a boolean value (true/false) and according to the result, adding (or not) a heading…

<?php if (is_search()) { ?>
	<h2 id="pagetitle">You searched for: <?php the_search_query(); ?></h2>
<?php } ?>

Roughly speaking, doing it this way is the better programming practice – if nothing else, there’s fewer files to go through and update if you want to make a small change in display etc. later. But best to get your head round both ways of doing it – there will be times when one or the other will be better suited to the purpose.

One slight gotcha, that’s fortunately receding into the mists of time, concerns is_home() and what happens if a static page is used as the index. Different, older, versions of WordPress will still produce variable results here – since WP2.5 the favoured test for the default home is is_front_page() – but you can’t guarantee what version of WordPress your theme might be used with, so some caution here…

And lastly, in the usual – slightly idiosyncratic – WordPress way, these are still referred to as Conditional Tags, just to create a small confusion with tags that are tags…

Next, a look at what can happen when a few values are plugged into these functions.