There’s one primary distinction between Drupal and WordPress. In Drupal, URLs map to PHP functions. In WordPress, URLs map to documents (or, quite often, collections of documents). The former can certainly be powerful and easy to work with. The latter, once you get used to the paradigm, can provide an incredible simplicity, powerful in its own way.
I was building a website today that has a location-based search component. Basically, I have a collection of posts with addresses, and I need to be able to search for addresses within a given distance of a queried address, and sort them by said distance. To be honest, that’s hard to do with WordPress. But it is possible…
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Building on my previous post about creating archive pages for custom post types, there’s another piece to add to the puzzle.
You archives pages will use the default index.php template. If you want to use a different template, you’ll need to hook into the template_redirect action to specify your template file. I like to use a file name like type-MY_POST_TYPE.php (although that’s easily changed), using the function below.
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When you create a new post type in WordPress using register_post_type(), WordPress does not automatically create a page for listing the archives of that post type. It’s possible to create one, though, without too much hassle.
For example, you can create an post type called article, and set the permalink for that post type to articles (i.e., an article will have a URL like http://example.com/articles/my-article-title).
Where do you go for a list of all articles, though? You might assume http://example.com/articles/, but you would be assuming erroneously. You could create a page with the slug articles and use a custom template for that page, but that doesn’t work with paging (e.g., http://example.com/articles/page/2/).
Instead, you need to fiddle with WordPress’s rewrite rules. (And thanks to Andrew Wilson for helping me understand this.)
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Update 2010-10-04: See Understanding Rewrite Tags for a somewhat more helpful treatment of the subject.
I’ve been playing around with WordPress 3.0 to create a bug/issue-tracking plugin (i.e., using WP to track bugs, not to track WP bugs (although it could conceivably do that)). More details about the plugin will be forthcoming, but now is as good a time as any to share the solution to one problem I came across.
Creating New Post Types and Taxonomies
When you create a new post type, you use the register_post_type function. When you create a new post type through that function, WP creates a new rewrite rule base on the name you give the post type. In my case, I’ve created an issue post type, so all issues, by default, will have the permalink /issue/%issue%/ (where %issue% is replaced with the post slug). Using the rewrite argument to register_post_type, you can change the beginning of the permalink to something different (e.g., /bugs/%issue%/) should you so desire.
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When you upload images into WordPress, it automatically creates smaller derivative images to serve as thumbnails. You have little control over these derivatives, aside from setting their maximum dimensions. If you upload any non-image media (e.g., a PDF, a video, an MP3, a tarball, etc.), you don’t get any thumbnail, for fairly obvious reasons.
Let’s say you want more control over your image thumbnails, or you would like to have thumbnails attached to your other uploads. You would need to install a plugin like the Custom Thumbnails plugin I just wrote.
What it does
WordPress associates each upload with a post or a page, using the item’s post_parent attribute. This plugin adds a field to the editing screen for your upload, allowing you to associate it with a “Parent Item”. Once thus associated, any time WordPress requests the thumbnail image of the parent item, it will retrieve the thumbnail image you uploaded, instead.
How it works
Writing this plugin took me much farther into the bowels of WordPress than I had reached before. As it turns out, I needed to use four completely undocumented filters to achieve the effect I wanted. Continue reading →
