PHP Utility Functions: get_value_or_default

Some handy functions I use to grab values from arrays and objects (especially $_REQUEST and friends), without having to constantly run isset or !empty checks everywhere (to avoid undefined index notices). You can specify a default value if the index doesn’t exist in the array or object. Also lets you sanitize the value(s) using a callback before returning them.

Note: No amount of helper functions will protect you from Bad Things. Always validate/sanitize untrusted data.

$var ) ? $object->$var : $default;
	elseif( is_array( $object ) )
		$value = ! empty( $object[$var] ) ? $object[$var] : $default;
		$value = $default;

	if( is_callable( $sanitize_callback ) ) {
		if( is_array( $value ) )
			$value = array_map( $sanitize_callback, $value );
			$value = call_user_func( $sanitize_callback, $value );

	return $value;

function get_request_var( $var, $default = '', $sanitize_callback = '' ) {
	return get_value_or_default( $var, $_REQUEST, $default, $sanitize_callback );
function get_get_var( $var, $default = '', $sanitize_callback = '' ) {
	return get_value_or_default( $var, $_GET, $default, $sanitize_callback );
function get_post_var( $var, $default = '', $sanitize_callback = '' ) {
	return get_value_or_default( $var, $_POST, $default, $sanitize_callback );

WordPress Tip: Using the same template across multiple category, tag, and author pages

Sharing Category Templates

Sharing Category Templates

Update (2009-12-21): So, the original technique that I had posted is a bit hacky and kinda gets annoying when you have lots of categories and category templates. There’s a better approach that can add to your functions.php file to make everything work magically, which was inspired by Justin Tadlock‘s comment on a post by Elliot Jay Stocks. Code below:

Add to your theme’s functions.php file and edit as necessary. For example, to redirect to categories with IDs 1 & 5 to a template called gallery.php, change the if statement to:

if( is_category( array( 1, 5 ) ) )
    template = locate_template( array( 'gallery.php', 'category.php' ) );

Easy, no?

Note: the stuff below is old, crappy, “legacy” code. Still here for posterity…

WordPress has an amazing theming system. It’s not perfect, but if you know the right things you can bend it to your will and do a lot of cool things. One great thing about it is the template hierarchy; WordPress basically allows you to create custom templates for categories, tags, authors, etc.

For example, if I add category.php to my theme, all category pages will now be styled according the structure within the category.php file. Now, let’s say I have a category called “Photos” that I wanted to look a little different from the rest. (Let’s assume the category ID for “Photos” is 6). All I have to do is add category-6.php to my theme, modify it to whatever, and the “Photos” category page will switch to this new template. Cool? Definitely.

With a system like this, you could technically customize your site to the point where the every category, author, tag, etc. page has a unique look and feel. But, that’s quite a lot of work and in most cases unnecessary. There may be cases though, where you want a small subset of categories to have a unique look, and you want these pages to share this look. Unfortunately WordPress doesn’t allow different pages to share templates. (Intuitively, I would think that something like creating a file called category-6,7,8.php [or similar] would apply this template to categories 6, 7, and 8). You could technically set up separate files (category-6.php / category-7.php / category8.php) and just copy and paste the code across all of them, but that’s a maintenance nightmare. A single change will have to be copied over multiple times, and that’s just annoying.

There are a few ways around this. One of easy ways is to use Idealion’s Category Enhancements plugin. Alternatively, if you want a more theme-level solution, follow the steps below. This is something I discovered while building out the image gallery pages for The Boar (links of what I came up with are at the bottom).

1. In your theme folder, create the category files for the categories you want to apply the custom template to.

  • Let’s assume we want to apply it to the categories “Portrait Photography” (ID: 5) and “Nature Photography” (ID: 12).
  • In this case we’d create category-5.php and category-12.php

2. In the category template files (category-5.php & category-12.php), add the following:

<?php require_once('common_template.php'); ?>

3. Create a generic category template: common_template.php

4. Then in the common_template.php, add the following:

<?php get_header(); ?>
<?php echo 'Hello World!'; ?>
<!-- The rest of your custom template goes here -->
<?php get_footer(); ?>

5. Now, if you navigate to and, you’ll notice that their look will mirror what you included in common_template.php

I should note that this approach isn’t limited to category templates; you can use this with author and tags templates as well. Technically, with this approach you could combine multiple categories and tags, as well (though if you do, be wary of category- and tag-specific functions and make use of conditional tags).

You can see an example of this in action at the links below:

Sample files you work from. Download them, rename the extension to .php and throw them into your template folder.

Thoughts, questions, suggestions? Leave a comment below or send me an email.