Can PHP take down a webserver? *HELP*

Can PHP take down a webserver? HELP

Anon

My webserver has been crashing ALOT over the past couple of days and the monkey's over @ the hosting company say it is because of one of my scripts. They will not however tell me what script it is, or give me access to there logs. Maybe someone on here can help me...

Here are the only 2 documents I have modified in a month

FIRST

  $start_time=microtime();

 $direct = "pictures/$dir/images";

$i=0;

$handle=opendir($direct);

while (false!=($file = readdir($handle))) {

if ($file != "." && $file != "..") { 

   print "<td><a href=# onClick=\"imgWindow=window.open('pictures/$dir/images/$file', 'image','width=660,height=500')\"><img src=pictures/$dir/thumbnails/$file border=0 width=100 height=75></a><br></td>";

  ++$i;

  if($i == $columns) { print "</tr><tr>"; 

  $i = 0;

  }

}

}

closedir($handle);

printf("</tr></table>");

$end_time=microtime();
$a=split(' ',$start_time.' '.$end_time);
$time=number_format((($a[2]+$a[3])-($a[0]+$a[1])),5);

printf(" <div align=center><font face=\"arial\" size=\"1\">Page Generated in: $time seconds</font></div> ");

That script simply generates a thumbnail gallery for $dir.

SECOND

$start_time=microtime();

/*--------- DATABASE CONNECTION INFO ---------*/
include("login.inc");

$i=0;
$c=1;
$color=cccccc;
$align=right;

$result = mysql_query("select * from pictures where year = '$year' order by date desc",$db);

while ($myrow = mysql_fetch_row($result)) {

$NAME=mysql_result($result,$i,"name");
$DATE=mysql_result($result,$i,"date");
$VENUE=mysql_result($result,$i,"venue");
$PROMOTER=mysql_result($result,$i,"promoter");
$TALENT=mysql_result($result,$i,"talent");
$DIRECTORY=mysql_result($result,$i,"directory");
$YEAR=mysql_result($result,$i,"year");
$IMAGE=mysql_result($result,$i,"image");

//// OPEN TABLE CELLS ////
if ($c == 1) {
printf("<tr><td valign=top bgcolor=$color>");
}
else {
if ($c == 2) {
printf("<td valign=top bgcolor=$color>");
}
else {
printf("<td valign=top bgcolor=$color>");
}
}

//// CONTENT OF THE TABLE CELLS ////
printf("<a href=\"eventimages.php3?dir=$YEAR/$DIRECTORY\"><img src=\"pictures/$YEAR/$DIRECTORY/thumbnails/$IMAGE\" align=\"$align\" border=\"0\" width=\"100\" height=\"75\"><font face=\"arial\" size=\"2\"><b>$NAME</b></font></a><font face=\"arial\" size=\"1\"><br>$DATE<br>$VENUE<br>$PROMOTER<br>$TALENT</font>");

//// CLOSE TABLE CELLS & ROTATE VARIABLES ////
if ($c == 1) {
printf("</td>");
$c=2; }
else {
if ($c == 2) {
printf("</td>");
$c=3; }
else {
printf("</td></tr>");
$c=1;
if ($align == right) { $align=left; }
else { $align=right; }
}
}
if ($color == cccccc) { $color=ffffff; }
else { $color=cccccc; }

++$i;

}

?>
<tr>
<td width="33%"> </td>
<td width="33%" align="center">
<?

//// PAGE GENERATION TIME ////

$end_time=microtime();
$a=split(' ',$start_time.' '.$end_time);
$time=number_format((($a[2]+$a[3])-($a[0]+$a[1])),5);

printf(" <font face=\"arial\" size=\"1\">Page Generated in: $time seconds</font> ");

this one simply generates a page based on my query...

any help is greatly appreciated....

thanks.
-m

Anon

What sort of server is it? I do know that (at least earlier) versions of PHP4, when run as an ISAPI module on Windows IIS can cause serious grief.

factory21

Check to see how PHP is installed. If it's as a CGI script, the chances are very low that your scripts are bringing down the server as the CGI version of PHP (and CGI scripts in general) more or less do not carry any state and are launched as separate processes. The only things I can think of that might take down a webserver via CGI is odd/malformed headers or extremely long data being returned from the script, possibly exposing bugs in the webserver. Again, the chances of this are very slim.

More likely, if PHP is installed as a module (as a DLL or .so), bugs in PHP can take down the webserver process. Theoretically, nothing in your script is supposed to be able to make PHP crash but sometimes doing odd operations (and not-so-odd ones) exposes bugs in the system.

Anon

Thanks, I will find out about that install info Eric.

The webserver is running some version of *nix w. apache as the webserver...

-m

Anon

Check for endless loops.

I can bring down Apache with an endless loop in PHP!!! (Multiple Apache's, multiple PHP's, Linux or Windoze {IIS/PWS or Apache}).

I'd look at all for(), foreach(), while(), etc. loops closely, first.

What happens is that something takes an inordinant amount of time, freezing the web server and causing is process to hang. At times, it requires a web server restart! It does not always happen, fortunately.

factory21

Yeah, this will probably bring down your server, although it shouldn't kill apache, especially if its configured correctly. PHP scripts also have a maximum execution time, the default of which is 30 seconds.

It should be pretty obvious if this is bringing the webserver down because the server will end up being heavily loaded and it will die in a more gradual death instead of a sudden one.

Mike Hoskins wrote:

Check for endless loops.

I can bring down Apache with an endless loop in PHP!!! (Multiple Apache's, multiple PHP's, Linux or Windoze {IIS/PWS or Apache}).

I'd look at all for(), foreach(), while(), etc. loops closely, first.

Anon

Even in less than 30 seconds an "endless" loop can cause problems, if PHP is demanding more and more system resources in the process, though again a properly configured server should simply abort script processing and free those resources back up instead of dying.

Anon

"In less than 30 seconds..." I'd have to agree -- less than the timeout in php.ini....

This might be a bug for the Zend guys to look into? If so, I wonder why this hasn't been brought up.

However, is there really anything like "an enless loop" checker, at runtime? I don't think so. Hence, the timeout value.

It would be nice if there was a mechanism to say, "this script should timout in 10 seconds," or "this look should abort in 5 seconds," etc., just to keep things stable on a heavily loaded web server.

Anon

Well, there is a set_time_limit() function you can call to set the timeout for a complete script, and a socket_set_timeout() for socket connections. Thing is, for finer-grained control (over individual blocks of code), you have to code for the situation where the timeout does occur, so that the whole script doesn't just go haywire.

As for an "infinite loop checker" - whether at runtime or compile time - I'm afraid that's a no-go. Certain special cases can be identified, but in general it's impossible (this is a fundamental result of computer science known as the "Halting Problem"). Hence the need for a timeout value in the first place.

Anon

I wasn't thinking of a Zend bug when I thought of scripts aborting before their timeout, I was thinking of scripts aborting before their timeout because there were insufficient resources to keep them running.