The WordPress conditional tags are some of the most powerful tools a theme designer can master. As WordPress themes get more complicated and more CMS like, everyone will eventually run into the need for conditionals. In my previous post I showed you how to write less code using conditional tags and the WordPress hierarchy. Quite a few things have changed since that post, and this time I’m going to show you some more advanced ways to use conditional tags.

What’s New?

The WordPress dev team heard the cries of the masses and has added new conditional tags to the core. A few include:

<?
is_front_page()
is_single(array(17,'beef-stew','Irish Stew'))
is_page(array(42,'about-me','About Me And Joe'))
is_page_template() ?>

Head on over to the codex conditionals page for a full list. The most important new tags are the ones which allow you to use arrays. In the past you may have had to use complex code to achieve the same result. The ability to filter content by several pages/categories/tags is incredibly useful especially in building large websites. The Codex does a good job at explaining the new tags so I won’t go into that here.

How’s Your PHP?

If you theme WordPress you probably know at least some basic PHP. The most basic and useful PHP you can learn are comparison operators. The operators will return true or false and work the same way as the WordPress conditional tags.

Let’s say you wanted some text to only show on the home page(ID is 42) and your about page. One way to do this is:

<?
if ( is_page( array (42,'About') ) ){
	echo "Hello World";
}

Lets say you didn’t know the ID of the page or the name, maybe it is in a theme and you want the user to set where the text appears. In this example $text_pages is a list set somewhere either by the user or some other function.

<?
$text_pages = get_option('pages');

if ( is_page( array($text_pages) ) ){
	echo "Hello World";
}

More complex examples

OK so far pretty basic stuff. Lets see something more complicated. We have text we want to show on a static home page, some posts in a certain category, but not in the search pages. Using PHP comparison operators and WordPress conditionals this is easy.

<?
if ( (is_front_page() || in_category('3') && !( is_search() ) ) {
	echo "Hello World";
}

Reading this in English goes like so: If is a static home page, or(||) in category 3 and(&&) is not(!) a search page. The exclamation mark is a shortcut for does not equal(!=).

As you can see developing complex conditionals can be very powerful, and can also save you from writing a bunch of repeated code. Lets take it even further and use some variables now.

Lets say you want the user to choose if there is a feature post displayed. You also want them to be able to set the categories used for a feature post. You also want don’t want the feature story repeating itself while paging. To accomplish this we’re going to use a combination of variables, WordPress conditionals, and some if else statements.

<?
$feature = get_option('feature');  // Gets the option to display feature post.
	if( ($feature == 'Yes') && !(is_paged()) ) { //Excludes the feature post when paging through posts
		$feature_cats = get_option('feature_cats'); // Gets list of feature categories
		query_posts(array('category__in' => array($feature_cats)));
		//The loop and post formatting
  	}

Making Your Own Conditionals

If you really want to get dirty, you can form your own conditionals. The Codex hints at this ability with this example:

!empty($post->post_excerpt) 

Pretty simple right? If the post excerpt is empty this will return false. Likewise removing the ! will then return false for anything that has an excerpt.

With a basic understanding of if else statements, and a not so basic understanding of WordPress functions you could create a conditional statement for just about anything granted you had something to compare to get a true or false statement.

Lets come up with another example. Say you want to display a special title whenever a post has approved comments.

<?php $foo = get_approved_comments($post->ID);
			if ( !empty($foo) ) {
				echo "<h1>I Gots Comments!</h1>";
				} ?>

Quick Comparison Operators Overview

The php comparison operators article goes into more detail but I’ll give you quick overview from a WordPress point of view.

When using these operators with WordPress conditional tags and if else statements keep track of your parenthesis! I’ve strung together quite a long string which ended in an equally long string of parenthesis, which will be a headache to decode later.

There are a few operators that are used more often. These are: equal( == ), not equal ( != ), or( || ), and( && ). Using these four you can construct some heavy conditionals.

Grouping is important! Just like math, you can group operators and conditionals to get different true or false statements. ex. (in_category(42) && !(is_search()) || is_archive())

Use !(), !empty(), empty() to achieve some more complex conditionals and create your own conditional statements.

The End

So there are some examples of complex WordPress conditionals, comparison operators, booleans, if elses, and some pie(update: I ate all the pie). This isn’t a complete list of what is possible, infact I don’t think it even scratches the surface. Conditionals are great, and are even more powerful than ever.