CHAPTER 5 ADDING AND CUSTOMIZING THEMES 161 The PHP code in template files rarely gets more complicated than this, and most of the time it will suffice if you can recognize which lines and bits belong together, so that you can copy and paste them without introducing errors. Tip To learn more about PHP code, read Beginning PHP5 and MySQL: From Novice to Professional,by W. Jason Gilmore (Apress, 2004). Template Variables Template files are the meeting place of static content (HTML) and dynamic values (variables), as well as minimal logic, similar to the examples shown in the previous section, to account for the numerous variations that are possible in a dynamic site. While there are many approaches and philosophies for templating in general, PHPTemplate has evolved in a way that encourages simple and minimal logic. It uses variables that are pushed into the template from the theme engine. Each template will have a number of variables available to it that are provided by the theme engine. In addition to the variables that are unique to each template, the variables $id and $zebra are always included by PHPTemplate, no matter which template is being called. These variables work as follows: $id: A sequential counter that is incremented every time the template is rendered. In the case of blocks, for example, it allows each block to have a unique ID on the page. $zebra: An alternating counter that has the value oddor even. This is useful for giving table rows alternating colors, for example. Furthermore, the variable $is_front is also available. It is true whenever the front page is being displayed, so you can always write template code like this: — display when on front page – PHPTemplate Template Files Here is an in depth look at the four tpl.php files included with PHPTemplate, as well as the page.tpl.php file that is included with the Bluemarine theme. Block.tpl.php The block.tpl.php file is included with the PHPTemplate engine and is therefore optional within individual themes. It is responsible for calls to theme(’block’) and generates the individual blocks within the various block regions. These are the blocks that you configure from the block administration page (admin/blocks). Table 5-4 lists the variables available in block.tpl.php.
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160 CHAPTER 5 ADDING AND CUSTOMIZING THEMES HTML code without needing to worry about escaping quotation marks or concatenating strings a fact that greatly improves the readability of template files over PHP functions that do the same thing. PHP Code and Templates If you are a web designer and you ve been given the task of creating a Drupal theme, you need not be scared of the fact that the templates mix PHP and HTML code. Even if you ve never programmed PHP before, the amount of skill and knowledge needed to work with the themes is small enough that you will be able to learn it quickly. Here are some examples of what you might see and explanations of what they do. The first is a simple printconstruct: This construct prints the contents of a variable (sends the contents to the browser for display on the screen). In this case, the variable $picture is being printed. The tags identify the parts that are to be interpreted as PHP and keep the PHP separate from the rest of the template. Here is a conditional print construct: This is a more elaborate version of the first example, which uses the ? and : to make a decision. In this case, it can be read if $sticky is set, print the text sticky; otherwise, print nothing (”"). The following uses if to make a decision:
In this example, the first line asks is $picture true? If so, the text
will be printed. Note that the opening if statement must be closed by a corresponding endif statement. Finally, this code creates a list:

This example shows how to build an unordered list

with a variable number of list items
• . It takes the variable $primary_links, which is an array, and uses the foreach operator to go over the array one item at a time, pointing the variable $link to the current item. For each primary link, an
• element with the link s contents is printed. Notice the endforeach tag, which is needed to close the foreach tag.
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CHAPTER 5 ADDING AND CUSTOMIZING THEMES 159 Exercise 5-1. Theme Breadcrumb Links Try your hand at overriding a themable function for the Bluemarine theme. Create a new file on your web server in the folder themes/bluemarine called template.php. Copy the following short code segment into the template.php file. Don t forget the .

Hello World!

‘; $output .= implode(’ / ‘, $breadcrumb); return $output; } ?> In the unaltered Bluemarine theme, breadcrumb links are separated using the character. This is the default HTML that is generated by Drupal. By including the phptemplate_breadcrumb function in the Bluemarine theme, the default HTML will no longer be used; instead, the HTML generated by the new function will be used. The phptemplate_breadcrumb function not only separates the breadcrumb links with a different character, but it also outputs a meaningful and original message directly above them. Click through some pages on your site and you will see the result. You have successfully altered the default HTML for breadcrumbs from this:

to this:

Hello World!

Home / create content Using Template Files In Exercise 5-1, you saw how a function could be written to override a themable function. As useful as this is, generating HTML from within functions can be very tiresome work. PHPTemplate makes the process of creating themable functions much easier and modular by introducing template files. The required file page.tpl.php is one such template file that will be used whenever theme(’page’) is called. This template must be provided by the theme itself. Other template files are provided by the PHPTemplate engine. These include block.tpl.php, box.tpl.php, comment.tpl.php, and node.tpl.php (see Figure 5-5 earlier in the chapter). These files override the block, box, comment, and node themable functions, respectively. If any of these four files appear in your theme folder alongside page.tpl.php, they will override the version in themes/engines/phptemplate. The template files are completely reusable; you could trade and mix the five standard tpl.php files between themes and expect, at a minimum, that they will be called at the appropriate time. Furthermore, since they are include files and not functions, you can write all the
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158 CHAPTER 5 ADDING AND CUSTOMIZING THEMES Theme engine s namespace: If the bluemarine namespace doesn t provide a function to theme foo, then Drupal looks to the theme engine namespace next. Assuming that Bluemarine is the active theme, the engine s namespace is phptemplate, as Bluemarine is a PHPTemplate theme. The function that Drupal will look for is therefore called phptemplate_foo($bar). Default namespace: Finally, if the function is not found in the engine s namespace, Drupal will use the default namespace, which is theme. A function named theme_foo($bar) will be called, and this is the function provided by the core include file or module. Thus, you can see that the default implementation of any themable function must begin with the prefix theme_. The active theme s own namespace is rarely used to override functions. You will not find many examples of bluemarine_foo, bluemarine_breadcrumb, and so on. Rather, you will see functions in the engine s namespace being written in the theme files. Anyone overriding a themable function is encouraged to take the engine s namespace to name the override functions. A strong and simple case can be made for this practice: if you want to move the function to a different theme or reuse it in some other way, you won t need to rename the function. Sticking with this policy will also allow you to copy whole theme directories and rename the directory, perhaps as the first step in creating a new theme. For the rest of the chapter, I will choose the option of naming themable functions after the theme engine and will not use the active theme s namespace. Note Pure themes (Chameleon) the themes that don t rely on an external theme engine are the exception to the advice of not using the active theme s namespace. If you need to override a theme function and you are using the Chameleon theme, you must use the Chameleon namespace. Table 5-3 shows some examples of common themable functions, what they would be named if overridden in the Bluemarine theme, and how they are evoked (parameters omitted). Table 5-3. Examples of Overriding Themable Functions in the Bluemarine Theme Default Version Bluemarine Version Invocation theme_links() phptemplate_links() theme(’links’) theme_submenu() phptemplate_submenu() theme(’submenu’) theme_xml_icon() phptemplate_xml_icon() theme(’xml_icon’) Exercise 5-1 demonstrates how to override a themable function.
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CHAPTER 5 ADDING AND CUSTOMIZING THEMES 157 theme_node($node, $teaser = FALSE, $page = FALSE): Provides the HTML wrapper for the content of a node. Based on the $teaser parameter, this function will return either the truncated preview version of a node or the full version. The $page variable determines whether the node is being displayed on its own page or in a list of nodes, and usually controls whether or not the title is printed as a heading. The function also handles calling theme_links() for any links that are to appear along with the node, such as taxonomy terms and whatever links have been added by modules, such as comment or subscription links. theme_comment($comment, $links = 0): Handles the output of comments. This includes comments made to posts like blogs as well as comments in a threaded forum. Note that this does not handle the threading itself, just the HTML around the variable $comment. Whatever links are associated with the comment are expressed in the variable $links. theme_block($block): Gets called for each block region and wraps the block content in HTML. theme_box($title, $content, $region = ‘main’): Builds a generic container around content, usually with the use of

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