Creating a new PHPTemplate
To create a new PHPTemplate, create a new directory under your themes directory, for example themes/mytheme (as of Drupal 6, your theme files should be stored in a new directory under sites/all/themes). Your theme's name should follow the same rules as other labels in PHP, i.e. it should start with a letter or underscore, followed by any number of letters, numbers, or underscores (no spaces, dashes, or special characters). Then, you need to create a file called page.tpl.php in that directory. Or you may copy an existing theme and just rename the directory. For Drupal 5, consider basing your theme on Zen or Blue breeze.
page.tpl.php is the only file which is absolutely required. It overrides the theme('page') function, which outputs the final page contents, along with all the extra decorations like a header, tabs, breadcrumbs, sidebars and a footer.
You can create files to override the following functions:
theme('page')(page.tpl.php): theme a pagetheme('block')(block.tpl.php): theme a block in sidebartheme('box')(box.tpl.php): theme a generic container for the main areatheme('comment')(comment.tpl.php): theme a commenttheme('node')(node.tpl.php): theme a node
The PHPTemplate package contains example template files for most of these, see box_grey for an example of page.tpl.php. Simply copy them into your theme/mytheme directory and edit them. Note that you will need to visit administer > themes for PHPTemplate to refresh its cache and recognize any new .tpl.php files.
If you want to theme a function other than the defaults listed here, you need to provide an override yourself.
