PHP从5.2升级到5.5后,根命令/代码无法正常工作

After an PHP upgrade from 5.2 to 5.5 (or newer) a friend's web site is not working anymore, regarding the host identifier ($DOCUMENT_ROOT).

He is using this code:

<?php
require("$DOCUMENT_ROOT/menulinks.inc.php");    
$status = $menu["home"]["id"];
require("$DOCUMENT_ROOT/header.inc.php");
?>
<div id="main">
<img src="images/miristart.jpg" alt="Startbild" style="margin-top 2%;"/>    
</div>
<?php 
require("$DOCUMENT_ROOT/footer.inc.php");
?>

And that is the error code:

Warning: require(/menulinks.inc.php): failed to open stream: No such file or directory in /www/htdocs/v137122/sedcard.php on line 2

Fatal error: require(): Failed opening required '/menulinks.inc.php' (include_path='.:/usr/share/php:..') in /www/htdocs/v137122/sedcard.php on line 2

So, do I have to use another command instead of $DOCUMENT_ROOT? Which one then? Thank you very much in advance.

First $DOCUMENT_ROOT is a variable.

During the update the PHP option register_globals was set to off. You can still access the document root through the $_SERVER array. This will look like $_SERVER ['DOCUMENT_ROOT'].