Tutorial : Theming Best Practices (Garland Gets a Cleanup)

Yesterday Garland got a long-overdue update: The page.tpl.php file was updated to use best practices. Now we can finally open up Garland in a workshop scenario and not have to use it as example of the bad practices within a .tpl.php file. This article applies to Drupal 6 and higher, though the theming principles apply to all versions of Drupal.

What's this about best practices? Let's compare the before and after of a few of the improvements. Each of the items below are extremely common things you can do to keep your .tpl.php files clean.
Avoiding Function Calls Directly in a .tpl.php file

The theme layer is a place where logic and markup should be clearly separated. The .tpl.php files should be used explicitly for markup, just printing out variables whenever necessary. Template.php can be used for any extensive stints of logic or anything more complicated that printing out a variable.

Before:
page.tpl.php
<!--[if lt IE 7]>
<?php print phptemplate_get_ie_styles(); ?>
<![endif]-->

After:
page.tpl.php
<!--[if lt IE 7]>
<?php print $ie_styles ?>
<![endif]-->

template.php
<?php
function garland_preprocess_page(&$vars) {
$vars['ie_styles'] = garland_get_ie_styles();
}
?>

The difference here is that all functions have been removed from page.tpl.php. Instead, we set a variable in template.php, then simply print out that variable in page.tpl.php. Note that this is in Drupal 6, in previous versions of Drupal the same thing would be done in the _phptempate_variables() function.

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Courtesy : Lullabot.com