Hướng dẫn ghi đè cho người mới bắt đầu Drupal

When someone talks about a Drupal theme, they are likely referring to the files of code bundled together and installed in the themes directory on your site. The theme 'code,' however, is not always located in the specific theme directory.

Consider the screenshots above. On the left are the files contained in the Stark theme (a theme that ships with Drupal 7). Observe that the Stark theme does not have any files that end with tpl.php. Why does this matter? Because it's the files that end with tpl.php that contain the HTML markup and PHP that make your webpages. There are several tpl.php files: html.tpl.php, page.tpl.php, node.tpl.php, block.tpl.php, etc. (When you have finished reading this tutorial, visit https://drupal.org/node/171194 for a visual depiction of the common tpl.php files and their purpose.)

In the right screenshot are the directories and files contained in the Bartik theme. Observe that the Bartik theme has a directory called templates. In that directory are files ending with tpl.php. (The next screenshot below shows the contents of the template directory.)

Question: How is it possible that Stark works without tpl.php files and Bartik has a directory with several?
Answer: Because "theme" in Drupal is not only pertain to the files within the theme directory.

The screen shot on the left lists the files and directory located in the node module, a core module located in the root modules directory. Notice that it contains a file called node.tpl.php. The node.tpl.php file contains the HTML markup that renders the node within the page that is displayed in your browser.

On the right is the template directory for the Bartik theme. Notice it contains five tpl.php files, including the node.tpl.php. You might be wondering why the Bartik theme has the node.tpl.php when the Stark theme does not. The answer is simple, the Bartik theme is overriding Drupal's default node.tpl.php file and the Stark theme is not.

How is this possible? That's the cool part. When a visitor to your site requests a page, let's say http://example.com/about-us, Drupal goes to work trying to find out what that page needs to look like. Amongst all the decisions it needs to make, based on your configurations, Drupal needs to know the HTML, PHP, CSS, etc. needed to present About Us as you planned.

• First it looks to the theme files. The theme files might be located in the root themes directory because you are using Bartik, Stark, or Garland. Or the theme files could be located in a directory at sites/all/themes/zeropoint, assuming you are using the Zero Point theme.
• If Drupal is trying to render a block for your About Us page and the theme you are using does not have the tpl.php that tells Drupal the markup, Drupal will go to the core block module and use the default block.tpl.php file located there.
• If Drupal is trying to display something (a page, a block) created by a contributed module, it will look to see if the module is providing the tpl.php. For example, if you have Views installed, take a look at the templates included in the module.

As we mentioned earlier, the Bartik theme is overriding Drupal's default node.tpl.php file (as well as four others). Let's see what this might look like. First, the developer of the Bartik theme copied the default node.tpl.php file into the Bartik theme template directory. Then she/he made the changes.

The screenshots compare the default node.tpl.php with Bartik's node.tpl.php. As you can see, Bartik has made some changes to the existing markup and added new markup.