This sliding doors CSS hack allows you to create sophisticated tabs for your navigation bar. Sadly, Wordpress core functions wp_list_pages() and wp_list_categories() don’t allow you to add the required span tag to use this technique.

We are going to see how to proceed in order to use sliding doors in our Wordpress theme.

Sliding doors, why?

There’s many articles available on the web about the sliding doors technique, so I’m not going to talk a lot about it. For people who don’t already know this famous hack, here’s a quick example.

Let’s build a typical navigation list:

<ul id="nav">
<li><a href="#">link n°1</a></li>
<li><a href="#">link n°2</a></li>
<li><a href="#">link n°3</a></li>
</ul>

If we apply, via CSS, background images to our links in order to make this menu prettier, we’ll quickly see a big problem: We must add a fixed width to the links, otherwise the image will be truncated if the link is too short, or the link will overflow the image if its width is too long.

That’s why sliding doors are very useful: We just have to add a span element inside the link, and then, in our CSS, assign a different background image to both the span element and the link.

<ul id="nav">
<li><a href="#"><span>link n°1</span></a></li>
<li><a href="#"><span>link n°2</span></a></li>
<li><a href="#"><span>link n°3</span></a></li>
</ul>

Our CSS should look like this:

#nav a, #nav a:visited {
display:block;
}
#nav a:hover, #nav a:active {
background:url(images/tab-right.jpg) no-repeat 100% 1px;
float:left;
}
#nav a span {
float:left;
display:block;
}
#nav a:hover span {
float:left;
display:block;
background: url(images/tab-left.jpg) no-repeat 0 1px;
}

Please note, as this is only an example, the CSS above isn’t complete and only shows how to apply the sliding doors hack.

You can see a live demo of a navigation menu which uses this technique on my blog here.

Using the sliding doors hack within Wordpress

I saw many blog posts where some users told you to modify Wordpress core in order to apply this technique. Personally, I never really liked this idea: First, the Wordpress core wasn’t made for being modified. And secondly, if you do, when you’ll upgrade your WP version, you’ll have to re-modify the core. Not user friendly at all!

Instead of this, let’s use a regular expression, by using the php preg_replace() function. We are going to get our pages (or categories) without displaying it, and passing it as a parameter to preg_replace(). The two remaining parameters will be, of course, our regular expression: The pattern we’re looking for, and this pattern’s replacement.

To create this menu, paste the following code instead of the wp_list_pages() (or wp_list_categories()) function in the header.php of your Wordpress theme.

To list your pages:

<ul id="nav">
<li><a href="<?php echo get_option('home'); ?>/"><span>Home</span></a></li>
<?php echo preg_replace('@\<li([^>]*)>\<a([^>]*)>(.*?)\<\/a>@i’, ‘<li$1><a$2><span>$3</span></a>’, wp_list_pages(’echo=0&orderby=name&exlude=181&title_li=&depth=1′)); ?>
</ul>

To list your categories:

<ul id="nav">
<li><a href="<?php echo get_option('home'); ?>/"><span>Home</span></a></li>
<?php echo preg_replace('@\<li([^>]*)>\<a([^>]*)>(.*?)\<\/a>@i’, ‘<li$1><a$2><span>$3</span></a>’, wp_list_categories(’echo=0&orderby=name&exlude=181&title_li=&depth=1′)); ?>
</ul>

Right now, your new menu is ready. You just have to make it sexy with CSS. Have fun!

This guest post was written by Jean-Baptiste Jung, who maintains a blog (written in French) that covers WordPress. If you have webmaster or WordPress knowledge and are interested in writing a post for Hack WordPress, please contact us.

Tired of your old navigation? So, what about creating a Magazine-style drop-down menu?
I propose here a drop-down menu listing your pages and sub pages, including one last item to show up your categories directly in the menu.

HTML and PHP

We will start by using WordPress core functions in order to retrieve our pages and categories. Edit the header.php of your theme, and replace your old nav code by this one:

<ul id="nav" class="clearfloat">
<li><a href="<?php echo get_option('home'); ?>/" class="on">Home</a></li>
<?php wp_list_pages('title_li='); ?>
<li class="cat-item"><a href="#">Categories</a>
<ul class="children">
<?php wp_list_categories('orderby=name&title_li=');
$this_category = get_category($cat);
if (get_category_children($this_category->cat_ID) != "") {
echo "<ul>";
wp_list_categories('orderby=id&show_count=0&title_li=
&use_desc_for_title=1&child_of='.$this_category->cat_ID);
echo "</ul>";
}
?>
</ul>
</li>
</ul>

This code will make a list of all our pages and subpages, as well as a last list element named “Categories”. When an user will hover top level pages (in case of a page menu) or top level categories, we will show up the related sub pages/categories.

CSS

Even if the code is fully functional, our script needs a good CSS styling. This CSS, which was taken from Darren Hoyt’s free Mimbo Theme, is perfect for what we want to do.

#nav{
background:#222;
font-size:1.1em;
}
#nav, #nav ul {
list-style: none;
line-height: 1;
}
#nav a, #nav a:hover {
display: block;
text-decoration: none;
border:none;
}
#nav li {
float: left;
list-style:none;
border-right:1px solid #a9a9a9;
}
#nav a, #nav a:visited {
display:block;
font-weight:bold;
color: #f5f5f4;
padding:6px 12px;
}
#nav a:hover, #nav a:active, .current_page_item a, #home .on {
background:#000;
text-decoration:none
}
#nav li ul {
position: absolute;
left: -999em;
height: auto;
width: 174px;
border-bottom: 1px solid #a9a9a9;
}
#nav li li {
width: 172px;
border-top: 1px solid #a9a9a9;
border-right: 1px solid #a9a9a9;
border-left: 1px solid #a9a9a9;
background: #777;
}
#nav li li a, #nav li li a:visited {
font-weight:normal;
font-size:0.9em;
color:#FFF;
}
#nav li li a:hover, #nav li li a:active {
background:#000;
}
#nav li:hover ul, #nav li li:hover ul, #nav li li li:hover ul, #nav li.sfhover ul, #nav li li.sfhover ul, #nav li li li.sfhover ul {
left: auto;
}
a.main:hover {
background:none;
}

Javascript

Modern browsers (Safari, Firefox, Opera, and even Internet Explorer 7) will not have any problem with the :hover pseudo-class on li elements. But as we can easily guess it, the obsolete IE6 can’t deal with that.

In order to make our script compatible with IE6, we’ll need to charge this little unobtrusive Javascript code, in the head section our our HTML document, or even better, in a separate .js file.

<![CDATA[//><!--
sfHover = function() {
var sfEls = document.getElementById("nav").getElementsByTagName("LI");
for (var i=0; i<sfEls.length; i++) {
sfEls[i].onmouSEOver=function() {
this.className+=” sfhover”;
}
sfEls[i].onmouSEOut=function() {
this.className=this.className.replace(new RegExp(” sfhover\\b”), “”);
}
}
}
if (window.attachEvent) window.attachEvent(”onload”, sfHover);
//–><!]]>

Now, your new drop-down menu is ready and will give your blog a professional look.