A WordPress template tag is made up of three components:
These are explained below.
WordPress is built with the PHP scripting language. Though you certainly don't need to be a PHP developer to use it, knowing a little about the language can go a long way in getting the most out of WordPress. Here we provide a tiny bit of that PHP knowledge:
The above shows the opening (<?php) and closing (?>) tag elements used to embed PHP functions and code in a HTML document, i.e. web page. There are a number of ways to embed PHP within a page, but this is the most "portable," in that it works on nearly every web server—as long as the server supports PHP (typically a document's filename also needs to end with the extension .php, so the server recognizes it as a PHP document).
Anything within this tag is parsed and handled by the PHP interpreter, which runs on the web server (the interpreter is the PHP engine that figures out what the various functions and code do, and returns their output). For our purposes, the PHP tag lets you place WordPress functions in your page template, and through these generate the dynamic portions of your blog.
A WordPress or template function is a PHP function that performs an action or displays information specific to your blog. And like a PHP function, a WordPress function is defined by a line of text (of one or more words, no spaces), open and close brackets (parentheses), and typically a semi-colon, used to end a code statement in PHP. An example of a WordPress function is:
the_ID() displays the ID number for a blog entry or post. To use it in a page template, you slip it into the PHP tag shown above:
<?php the_ID(); ?>
This is now officially a WordPress template tag, as it uses the PHP tag with a WordPress function.
The final item making up a template tag is one you won't necessarily make use of unless you want to customize the tag's functionality. This, or rather these, are the parameters or arguments for a function. Here is the template function bloginfo(), with the show parameter being passed the 'name' value:
<?php bloginfo('name'); ?>
If your blog's name is Super Weblog, the bloginfo() template tag, when using 'name' as the show parameter value, will display that name where it's embedded in your page template.
Not all template tags accept parameters (the_ID() is one), and those which do accept different ones based on their intended use, so that the_content() accepts parameters separate from those which get_calendar() can be passed.
See the following Codex pages for more information on WordPress templates and template tags: