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XHTML and template.php

Submitted by Shelley on Sun, 06/08/2008 - 22:37

Since I use inline SVG in all of my sites, I need to serve my pages up as XHTML. I couldn't find a Drupal module or option that triggers Drupal to serve the pages up as XHTML, so I added the following code at the very top of the page.tpl.php page:

<?php
header("Vary: Accept");
if (stristr($_SERVER["HTTP_ACCEPT"], "application/xhtml+xml"))
    header("Content-Type: application/xhtml+xml; charset=utf-8");
else
    header("Content-Type: text/html; charset=utf-8");
?>

All this code does is check whether the user agent can support XHTML. If it can, the page is served up as XHTML; otherwise HTML. Using embedded PHP in page.tpl.php for the theme works as desired. However, the content type of the page no longer agrees with the content-type meta element, which is included within the $head variable.

  <head>
    <title><?php print $head_title ?></title>
    <?php print $head ?>
    <?php print $styles ?>
    <?php print $scripts ?>
    <!--[if lt IE 7]>
      <?php print phptemplate_get_ie_styles(); ?>
    <![endif]-->
  </head>

One solution would be to not print out the $head variable and just hard code all of the head entries. However, when you add a new module, such as the RDF module, which adds entries to the $head variable, you either have to hard code these in, also, or you lose functionality.

Instead, I used the template.php file, which is used to override default Drupal behavior. Specifically, I created a variant of _preprocess_page for my subtheme, used this to access $head, and alter it.

function flame_preprocess_page(&$vars) {
  $head = $vars['head'];
  $head = str_replace("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" />",
              "<meta http-equiv=\"Content-Type\" content=\"application/xhtml+xml; charset=UTF-8\" />", $head);

  $head = str_replace("<link rel=\"alternate\" type=\"application/rss+xml\" title=\"Burningbird's RealTech RSS\" href=\"http://realtech.burningbird.net/rss.xml\" />\n","",$head);

  $vars['head'] = $head;
}

I am still getting my head around customization in Drupal, and will have a follow up posting later, after I've had more time to work through issues. In the meantime, from my understanding, the _preprocess_page passes in an array of system variables, each of which can be accessed and altered, as I've done in the code example. The subtheme naming is essential, otherwise I would overwrite the use of the function within the Garland theme.

There is another theme specific function for overriding variables called _phptemplate_variables, but I gather that was Drupal 5 and the approach I used is Drupal 6.x and forward.

Now, the head entries are as I want them, and modules such as RDF can add their entries without me impacting on their work. More importantly, with the addition of the XHTML support, I can add inline SVG and the SVG will display correctly for those browsers that support inline SVG.

Hello, World!