The start of webdav.php should be something along the lines of:

if ( version_compare( phpversion(), '5.2' ) < 0 )
{
error_log( "Unsupported PHP version " . phpversion() .". eZ Publish 4.x does not run with PHP 4");
header( "HTTP/1.1 404 Not Found" );
print ( "WebDAV functionality is disabled!" );
exit;
}

require 'autoload.php';

ignore_user_abort( true );
ob_start();

BTW: index.php mentions 'eZ Publish 3.x' instead of '4.x'...