Why are php tags not closed in drupal?

This is the code in `index.php`,with only `<?php`,but no `?>`,this is my first time to see code like this,any reason?

<?php
// $Id: index.php,v 1.94 2007/12/26 08:46:48 dries Exp $

/**
* @file
* The PHP page that serves all page requests on a Drupal installation.
*
* The routines here dispatch control to the appropriate handler, which then
* prints the appropriate page.
*
* All Drupal code is released under the GNU General Public License.
* See COPYRIGHT.txt and LICENSE.txt.
*/

require_once './includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

$return = menu_execute_active_handler();

// Menu status constants are integers; page content is a string.
if (is_int($return)) {
switch ($return) {
case MENU_NOT_FOUND:
drupal_not_found();
break;
case MENU_ACCESS_DENIED:
drupal_access_denied();
break;
case MENU_SITE_OFFLINE:
drupal_site_offline();
break;
}
}
elseif (isset($return)) {
// Print any value (including an empty string) except NULL or undefined:
print theme('page', $return);
}

drupal_page_footer();

Omitting the closing tag prevents the accidental injection of trailing white space into the response.

Is a common coding practice in some Frameworks, like [Zend][1].


[1]:

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Omitting PHP closing tags is part of the [Drupal Coding Standards][1].

Ever since Drupal 4.7, the ?> at the end of code files is purposely omitted. This includes for module and include files. The reasons for this can be summarized as:

- Removing it eliminates the possibility for unwanted whitespace at the end of files which can cause "header already sent" errors, XHTML/XML validation issues, and other problems.
- The [closing delimiter at the end of a file is optional][2].
- PHP.net itself removes the closing delimiter from the end of its files (example: [prepend.inc][3]), so this can be seen as a "best practice."

[1]:

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[2]:

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[3]:

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