sometimes when i click on a link the php-script returns no data, so a blank page is displayed. this error just happens sometimes. not regular. also this happens more often when i submit a <form> (doesn't matter if POST oder GET method).

here an example script (index.php):

<?
include("include/server.php");
include("include/settings.php");

$oPage = new XTemplate ("html/root.html");

switch ($what) {
	case "ha":		$sTitel	=	"home &amp; aktuelles";																	$sInhalt =	include("news.php");		break;
	case "lpp_p":	$sTitel	=	"leistungen preise &amp; produkte - printlayout";										$sInhalt =	include("lpp_p.php");		break;
	case "lpp_sp":	$sTitel	=	"leistungen preise &amp; produkte - spieleprogrammierung";								$sInhalt =	include("lpp_sp.php");		break;
	case "lpp_wh":	$sTitel	=	"leistungen preise &amp; produkte - webhosting";										$sInhalt =	include("lpp_wh.php");		break;
	case "lpp_ipm":	$sTitel	=	"leistungen preise &amp; produkte - internet projekt &amp; beteiligungs management";	$sInhalt =	include("lpp_ipm.php");		break;
	case "lpp_ssn":	$sTitel	=	"leistungen preise &amp; produkte - software, server &amp; netzwerktechnik";			$sInhalt =	include("lpp_ssn.php");		break;
	case "lpp_os":	$sTitel	=	"leistungen preise &amp; produkte - online shop";										$sInhalt =	include("lpp_os.php");		break;
	case "lpp_ie":	$sTitel	=	"leistungen preise &amp; produkte - internet entwicklung";								$sInhalt =	include("lpp_ie.php");		break;
	default:		$sTitel	=	"home &amp; aktuelles";																	$sInhalt =	include("news.php");		break;
}

if ($what == "ha" || !$what) {
	if (!$show) {
		$oPage->parse("root.fragen");
	}
}

$oPage->assign("FILE",		$PHP_SELF);
$oPage->assign("TITEL",		$sTitel);
$oPage->assign("INHALT",	$sInhalt);

$oPage->parse("root");
$oPage->out("root");
?>

the file "server.php" just checks on which server the script is running an sets the include_path and global mysql-access variables. and it includes 5 more php files which contains classes and functions.

the file "settings.php" has the following content:
<?
set_time_limit(0);

header ("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header ("Last-Modified: " . gmdate ("D, d M Y H:i:s") . " GMT"); 
header ("Cache-Control: no-cache, must-revalidate");
header ("Pragma: no-cache");

session_register("sLanguage");
?>

when i remove the header-data the problem still exists.

also i tried the following in my "index.php"

<?
include("include/server.php");
include("include/settings.php");
?>
<div></div>
<?
$oPage = new XTemplate ("html/root.html");

if ($what == "ha" || !$what) {
	if (!$show) {
		$oPage->parse("root.fragen");
	}
}

$oPage->assign("FILE",		$PHP_SELF);
$oPage->assign("TITEL",		$sTitel);
$oPage->assign("INHALT",	$sInhalt);

$oPage->parse("root");
$oPage->out("root");
?>

the problem still exists ...

i use apache 1.3.26.