Description:
------------
Encountering a memory leak, possibly in date/time related code.

Running this script:
=================================================================
<?php

// tell us about all errors.
error_reporting(E_ALL);

define ("START_YEAR", 1971);
define ("END_YEAR",   2038);

function test_strtotime($request) {
  for ($i=1; ; $i++) {
    // start at year START_YEAR, bail out at year END_YEAR
    $tStamp = mktime (17,17,17,1,$i,START_YEAR);
    if (date("Y", $tStamp) == END_YEAR) break;
    $strtotime_timestamp = strtotime ($request, $tStamp);           
    if (strftime("%r %B %d %Y", $strtotime_timestamp) != date ("h:i:s A F d Y", $strtotime_timestamp)) {
      print "Mismatch: $i $tStamp\n";
    }
  }
}

$days = array ("Monday", "Tuesday", "Wednesday",
               "Thursday", "Friday", "Saturday", "Sunday");

for ($i=1; $i<500; $i++) {
  putenv("TZ=Australia/Sydney");
  foreach ($days as $day) {
    test_strtotime($day);
  }
}                

?>
=================================================================

What's different to various other scripts I've run before to test date/time code is this line:
> if (strftime("%r %B %d %Y", $strtotime_timestamp) != date ("h:i:s A F d Y", $strtotime_timestamp))
So, something about this may possibly be the culprit.

Here's what I see on a Linux box whilst running this:
=================================================================
ludo:~/tmp/php-5.1-dev# date; free; ps auxw | grep php
Fri Jul  8 15:46:29 EST 2005
             total       used       free     shared    buffers     cached
Mem:        452324     449108       3216          0      13016     325608
-/+ buffers/cache:     110484     341840
Swap:       787144          0     787144
root      1906 99.9  9.7 46796 44012 ttyp1   R+   15:46   0:15 /root/tmp/php-5.1-dev/php5-200507080430/sapi/cli/php ./poss-memory-leak.php
ludo:~/tmp/php-5.1-dev# date; free; ps auxw | grep php
Fri Jul  8 15:46:37 EST 2005
             total       used       free     shared    buffers     cached
Mem:        452324     449516       2808          0       9904     307260
-/+ buffers/cache:     132352     319972
Swap:       787144          0     787144
root      1906 99.9 14.5 68728 65944 ttyp1   R+   15:46   0:23 /root/tmp/php-5.1-dev/php5-200507080430/sapi/cli/php ./poss-memory-leak.php
ludo:~/tmp/php-5.1-dev# date; free; ps auxw | grep php
Fri Jul  8 15:46:52 EST 2005
             total       used       free     shared    buffers     cached
Mem:        452324     449276       3048          0       6160     270252
-/+ buffers/cache:     172864     279460
Swap:       787144          0     787144
root      1906 99.9 23.6 109604 106820 ttyp1 R+   15:46   0:38 /root/tmp/php-5.1-dev/php5-200507080430/sapi/cli/php ./poss-memory-leak.php
ludo:~/tmp/php-5.1-dev# date; free; ps auxw | grep php
Fri Jul  8 15:47:23 EST 2005
             total       used       free     shared    buffers     cached
Mem:        452324     448996       3328          0       4920     190460
-/+ buffers/cache:     253616     198708
Swap:       787144         64     787080
root      1906 99.9 41.5 190912 188132 ttyp1 R+   15:46   1:09 /root/tmp/php-5.1-dev/php5-200507080430/sapi/cli/php ./poss-memory-leak.php
root      1922  0.0  0.0  1344  440 ttyp0    R+   15:47   0:00 grep php
ludo:~/tmp/php-5.1-dev# date; free; ps auxw | grep php
Fri Jul  8 15:47:36 EST 2005
             total       used       free     shared    buffers     cached
Mem:        452324     449316       3008          0       4872     159064
-/+ buffers/cache:     285380     166944
Swap:       787144         64     787080
root      1906 99.9 48.7 223104 220320 ttyp1 R+   15:46   1:22 /root/tmp/php-5.1-dev/php5-200507080430/sapi/cli/php ./poss-memory-leak.php
ludo:~/tmp/php-5.1-dev# date; free; ps auxw | grep php
Fri Jul  8 15:48:26 EST 2005
             total       used       free     shared    buffers     cached
Mem:        452324     449508       2816          0       1036      35880
-/+ buffers/cache:     412592      39732
Swap:       787144         64     787080
root      1906 99.9 78.3 357200 354420 ttyp1 R+   15:46   2:13 /root/tmp/php-5.1-dev/php5-200507080430/sapi/cli/php ./poss-memory-leak.php
root      1930  0.0  0.0  1344  444 ttyp0    S+   15:48   0:00 grep php
ludo:~/tmp/php-5.1-dev# date; free; ps auxw | grep php
Fri Jul  8 15:48:56 EST 2005
             total       used       free     shared    buffers     cached
Mem:        452324     448796       3528          0         80       8272
-/+ buffers/cache:     440444      11880
Swap:       787144      75912     711232
root      1906 99.9 81.1 435200 366960 ttyp1 R+   15:46   2:41 /root/tmp/php-5.1-dev/php5-200507080430/sapi/cli/php ./poss-memory-leak.php
root      1934  0.0  0.0  1344  444 ttyp0    S+   15:49   0:00 grep php
ludo:~/tmp/php-5.1-dev# date; free; ps auxw | grep php
Fri Jul  8 16:00:25 EST 2005
             total       used       free     shared    buffers     cached
Mem:        452324     449584       2740          0         80       1076
-/+ buffers/cache:     448428       3896
Swap:       787144     787144          0
root      1906 42.7 95.1 1216916 430252 ttyp1 T   15:46   7:40 /root/tmp/php-5.1-dev/php5-200507080430/sapi/cli/php ./poss-memory-leak.php
root      1957  0.0  0.0  1348  320 ttyp0    S+   16:01   0:00 grep php
=================================================================

After 14 minutes the box was thrashing to disk and was extremely slow to respond. Suspending the script (ctrl-Z), and checking the output of 'top' showed that php was using around a gigabyte of RAM:
=================================================================
Tasks:  40 total,   2 running,  37 sleeping,   1 stopped,   0 zombie
Cpu(s):  0.3% us,  0.0% sy,  0.0% ni, 97.3% id,  2.3% wa,  0.0% hi,  0.0% si
Mem:    452324k total,   446624k used,     5700k free,      448k buffers
Swap:   787144k total,   787144k used,        0k free,     5008k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                      
 1906 root      18   0 1188m 419m 4200 T  0.0 95.0   7:40.77 php                                                          
 2398 root      16   0  1788  960 1664 R  0.0  0.2   0:00.06 top                                                          
  861 root      16   0  6460  592 6016 R  0.0  0.1   0:03.96 sshd                                                         
  877 root      16   0  2244  424 2080 S  0.0  0.1   0:01.67 bash  
[ ... snip ... ]                   
=================================================================

And when left running, it eventually gives out-of-memory messages like this in the kernel log:
=================================================================
Jul  7 17:49:37 ludo kernel: Out of Memory: Killed process 818 (apache).
Jul  7 17:50:25 ludo kernel: Out of Memory: Killed process 819 (apache).
Jul  7 17:53:34 ludo kernel: Out of Memory: Killed process 861 (apache).
Jul  7 17:57:50 ludo kernel: Out of Memory: Killed process 573 (mysqld).
Jul  7 17:57:50 ludo kernel: Out of Memory: Killed process 575 (mysqld).
Jul  7 17:57:50 ludo kernel: Out of Memory: Killed process 576 (mysqld).
Jul  7 17:57:50 ludo kernel: Out of Memory: Killed process 577 (mysqld).
Jul  7 18:02:58 ludo kernel: Out of Memory: Killed process 1284 (apache).
Jul  7 18:03:17 ludo kernel: Out of Memory: Killed process 1285 (apache).
Jul  7 18:03:23 ludo kernel: Out of Memory: Killed process 1259 (php).
=================================================================