I need some php to output the time in various cities around the world (London, Hong Kong, Bangkok etc), and automatically take account for daylight saving times etc...

Any easy ways to do this?

I've tried a few readymade scripts but can't get this to work yet (PHP4 and not 5)

This actually is a bit of an issue, I think what my co-worker did was base the output off the offset... like +3 for eastern time or whatever. I don't think it accounts for time zone changes though. You can... maybe... scrape the output of http://whattimeisit.com/cgitime.exe?Mode=FullList one a day, store the offsets for each place, and then use the time function and add an hour or whatever accordingly.

I use this for getting the GMT on the server I'm on:

//getting timezone variables so polling date is correct
$longOffset = shell_exec('ls -l /etc/localtime');

if (ereg("GMT+",$longOffset)) {
$gmt = split("GMT",$longOffset);
} else if (ereg("GMT-",$longOffset)) {
$gmt = split("GMT",$longOffset);
}
if (isset($gmt)){
$gmtNum = $gmt[1];
$gmtVar = trim("Etc/GMT".$gmt[1]);
}


Here's the dropdown I use to set the timezeone:
<?php
function checkOffset($checkVal,$gmtOffSet) {
if ($checkVal == $gmtOffSet) {
echo "selected=\"selected\"";
}
}
?>
<select name="timezone">
<option value="+12" <?php checkOffset(+12,$gmt[1]); ?>>GMT+12: IDLE/NZST</option>
<option value="+11" <?php checkOffset(+11,$gmt[1]); ?>>GMT+11:</option>
<option value="+10" <?php checkOffset(+10,$gmt[1]); ?>>GMT+10: GST</option>
<option value="+9" <?php checkOffset(+9,$gmt[1]); ?>>GMT+09: JST</option>
<option value="+8" <?php checkOffset(+8,$gmt[1]); ?>>GMT+08: CCT</option>
<option value="+7" <?php checkOffset(+7,$gmt[1]); ?>>GMT+07:</option>
<option value="+6" <?php checkOffset(+6,$gmt[1]); ?>>GMT+06:</option>
<option value="+5" <?php checkOffset(+5,$gmt[1]); ?>>GMT+05:</option>
<option value="+4" <?php checkOffset(+4,$gmt[1]); ?>>GMT+04:</option>
<option value="+3" <?php checkOffset(+3,$gmt[1]); ?>>GMT+02: EET</option>
<option value="+2" <?php checkOffset(+2,$gmt[1]); ?>>GMT+03: BT</option>
<option value="+1" <?php checkOffset(+1,$gmt[1]); ?>>GMT+01: CET</option>
<option value="+0" <?php checkOffset(0,$gmt[1]); ?>>GMT: GMT</option>
<option value="-1" <?php checkOffset(-1,$gmt[1]); ?>>GMT-01: WAT</option>
<option value="-2" <?php checkOffset(-2,$gmt[1]); ?>>GMT-02: AT</option>
<option value="-3" <?php checkOffset(-3,$gmt[1]); ?>>GMT-03:</option>
<option value="-4" <?php checkOffset(-4,$gmt[1]); ?>>GMT-04: AST</option>
<option value="-5" <?php checkOffset(-5,$gmt[1]); ?>>GMT-05: EST</option>
<option value="-6" <?php checkOffset(-6,$gmt[1]); ?>>GMT-06: CST</option>
<option value="-7" <?php checkOffset(-7,$gmt[1]); ?>>GMT-07: MST</option>
<option value="-8" <?php checkOffset(-8,$gmt[1]); ?>>GMT-08: PST</option>
<option value="-9" <?php checkOffset(-9,$gmt[1]); ?>>GMT-09: YST</option>
<option value="-10" <?php checkOffset(-10,$gmt[1]); ?>>GMT-10: AHST</option>
<option value="-11" <?php checkOffset(-11,$gmt[1]); ?>>GMT-11: NT</option>
<option value="-12" <?php checkOffset(-12,$gmt[1]); ?>>GMT-12: IDLW</option>
</select>


Maybe there's something in there that you can use.

I got some help with this on PHPBuilder.com.... you can use putenv like this pretty successfully:

<?php
$now = time(); // use this so all times are to the same second
$tz = getenv("TZ"); // save local setting so we can reset it later
putenv("TZ=GMT");
printf("<p>The GMT/UDT time is %s</p>\n", date('H:i:s', $now));
putenv("TZ=Europe/London");
printf("<p>The time in London is %s</p>\n", date('H:i:s', $now));
putenv("TZ=Asia/Dubai");
printf("<p>The time in Dubai is %s</p>\n", date('H:i:s', $now));
putenv("TZ=Asia/Hong_Kong");
printf("<p>The time in Hong Kong is %s</p>\n", date('H:i:s', $now));
putenv("TZ=$tz");
printf("<p>The local server time is %s</p>\n", date('H:i:s', $now));
?>

Also a list of supported timezones at http://www.php.net/manual/en/timezones.php :)