Understanding conditionals is an absolute must in creating unique WordPress sites. Like its name suggests the conditional tag allows you to display content depending on a specific condition.
The best place to start when learning how conditionals can be used is with page settings.
For example if you wanted to post a message of your home page or display a specific image, the following code would be added to your template file:
<?php if(is_front_page()) {?>
<p>This is our front page so we will do this.</p>
<?php } else {?>
<p>We're no longer on the front page, so we will do that instead.</p>
<?php } ?>
Display different content on your sidebar
Conditional tags also allow you to dress up your sidebar differently depending on where you are on your site. I find myself building lots of websites for clients who do not wish to modify their first level of navigation, but do have the need to modify subpages. Thus with the parent page in place, I use the following code in my sidebar to create the sidebar navigation for each section.
<ul>
<?php if(is_page(2) || $post->post_parent==2) {
wp_list_pages('sort_column=menu_order&child_of=2&depth=1&title_li=');
} elseif (is_page(3) || $post->post_parent==3) {
wp_list_pages('sort_column=menu_order&child_of=3&depth=1&title_li=');
} elseif (is_page(4) || $post->post_parent==4) {
wp_list_pages('sort_column=menu_order&child_of=4&depth=1&title_li=');
} elseif (!is_page()) {
wp_list_categories('title_li=');
}?>
</ul>
The page(#) correspond to the page ID. You could also use the slug if you prefer, but don’t forget to use single quotes.
Check to see if custom field exists
Conditional tags can also be used to check for things other than being a certain page. Testing to see if a custom field exist for example can be handy:
<?php while (have_posts()) : the_post();
$link=get_post_meta($post->ID, 'link', true);
if($link != '') {
echo '<a href="'.$link.'">';
echo the_post_thumbnail().'</a>';
}else {
the_post_thumbnail();
}
the_content();
endwhile; ?>
A similar example would be to check to see if a featured image has been uploaded and if not display a default one.
<?php if(has_post_thumbnail()) {
the_post_thumbnail();
} else {?>
<img src="<?php bloginfo('template_directory');?>/images/banner.gif" alt="">
<?php }?>
As you can see conditional tags are very handy. The examples above are some of my most used code snippets. Do you have any favourites?
I use these same ones a lot too. Also these:
is_category() – if you’re on a category page
is_category(1) – if you’re viewing category 1 page
in_category(1) – if the post you’re displaying is in category 1 (for example)
When you’re just learning this stuff it’s really helpful to read about them on the codex, e.g.
http://codex.wordpress.org/Function_Reference/is_category
And also, if the change you need to make is only a CSS change, view source and see which classes WordPress has inserted in the body tag. Those are really powerful all on their own.
Good one Z. I forgot about in_category. I recently build a site with two categories and switched the background colour of the site depending on the category they were in. Very handy.
Over on twitter, Andrew Norcross pointed out that he uses conditionals to enqueue jQuery on his front_page if needed using the following code.
function load_my_script() {
if( is_front_page() ) {
wp_enqueue_script(‘myscript’,”.get_bloginfo(‘template_directory’).’/lib/js/custom-script.js’,array(‘jquery’), false, false);
}
}
add_action(‘wp_print_scripts’, ‘load_my_script’);
That’s a handy code snippet I’ll be using.
Thanks Christine!
This example snippet of code will come in quite useful when trying to create my conditional tags!