I ran ApacheBench on a PEAR DB script (see below), and IIS (ISAPI mode) will die eventually. It is so bad that often "iisreset" is unable to restart IIS. 

The ab command I used:

ab -n10000 -c10 <url>

with the following results:

This is ApacheBench, Version 1.3c <$Revision: 1.45 $> apache-1.3
Copyright (c) 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Copyright (c) 1998-2000 The Apache Group, http://www.apache.org/

Server Software:        Microsoft-IIS/5.0
Server Hostname:        jaguar
Server Port:            80

Document Path:          /lens/adodb/peartest.php
Document Length:        142 bytes

Concurrency Level:      10
Time taken for tests:   269.158 seconds
Complete requests:      10000
Failed requests:        5272
   (Connect: 0, Length: 5272, Exceptions: 0)
Non-2xx responses:      1868
Total transferred:      1891906 bytes
HTML transferred:       769177 bytes
Requests per second:    37.15
Transfer rate:          7.03 kb/s received

Connnection Times (ms)
              min   avg   max
Connect:        0     0     5
Processing:     2   268  2771
Total:          2   268  2776


The interesting thing is that the crash only happens when an invalid SQL statement is entered in the script below(notice the column "badcolumn" which does not exist). If a valid SQL statement is entered ("badcolumn" is removed), no crash occurs, and ApacheBench runs fine. 

So I guess it is some problem with PHP's error-handler or MySQL extension not being thread safe. No dll extensions were installed. Standard pre-compiled PHP downloaded from php.net was used.

John Lim

======================= THE SCRIPT ===================

<?php

include "DB.php";

$DBNAME = 'PEAR DB';

$dsn = "mysql://root:@localhost/northwind";
$db = &DB::Connect($dsn);

$rs = $db->query('select badcolumn,productid,productname,unitsinstock,unitprice from products');
while (DB_OK === $rs->fetchInto($fields)) {
	$id=$fields[0];
	$name=$fields[1];
	$unitsinstock=$fields[2];
	$unitprice=$fields[3];
	
		print "$id, $name, $unitsinstock, $unitprice<br>";
}

$rs->free();

?>