Hi!
Here is the script that shows the time of the client system. I added
quite a bit of commentary to it, so it should be obvious what it does.
I wrapped it into a function, but that is not really necessary.
As mentioned earlier the core piece is the JavaScript, which I did not
create, but some smart person on the ECLUG mailing list. The rest may be
trivial to you, but I think it is darn smart and I'm proud of it. :)
Have fun and show your clients that you are ticking right.
David
<?php
function showclienttime() {
// -----------------------------------------------------------------------
// Define variables
// -----------------------------------------------------------------------
$fct_severtimedata = array();
$fct_servertime = "";
$fct_serverbias = 0;
$fct_clientbias = 0;
$fct_totalbias = 0;
$fct_clienttimestamp = 0;
$fct_year = "";
$fct_month = "";
$fct_day = "";
$fct_hour = "";
$fct_minute = "";
$fct_second = "";
// -----------------------------------------------------------------------
// Make nice time string following international standards
// Get client GMT bias
// JavaScript creates a cookie if it does not exists and writes the client
// GMT bias in it, then unfortunately reloads the page to read out the
// cookie value to have it available for PHP to pick up
// JavaScript contributed from a smart person of ECLUG
if(!isset($_COOKIE['GMT_bias'])) {
?>
<script type="text/javascript">
var Cookies = {};
/***
* @name = string, name of cookie
* @value = string, value of cookie
* @days = int, number of days before cookie expires
***/
Cookies.create = function (name, value, days) {
if (days) {
var date = new Date();
date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
var expires = "; expires=" + date.toGMTString();
} else {
var expires = "";
}
document.cookie = name + "=" + value + expires + "; path=/";
this[name] = value;
}
var now = new Date();
Cookies.create("GMT_bias",now.getTimezoneOffset(),7);
window.location = "<?php echo $_SERVER['PHP_SELF'];?>";
</script>
<?php
} else {
$fct_clientbias = $_COOKIE['GMT_bias'];
}
// Get server GMT bias
$fct_servertimedata = gettimeofday();
$fct_servertime = $fct_servertimedata['sec'];
$fct_serverbias = $fct_servertimedata['minuteswest'];
// Assume that the client is in the western european time zone (e.g.
Germany).
// That gives currently a bias for Eastern US of 240 and for Germany one of
-120.
// In this case one can subtract the -120 from the 240, which gives
240-(-120) = 360.
// This is correct as Germany is six hours ahead.
// Now the assumed client is in California and as such the GMT bias is 420.
// Calculating again gives 240 - (420) = -180
// This means that when the result is negative one has to subtract the
result from
// server time, otherwise one needs to add it. Math comes to help as that
// server time + (360) = server time + 360
// and
// server time + (-180) = server time - 180
// Finally 1 minutes has 60 seconds so the client/server bias has to be
multiplied
// by 60 and then added to the unix style time stamp for the current server
time
// Make total bias in minutes
$fct_totalbias = $fct_serverbias - $fct_clientbias;
// Transition total bias to seconds
$fct_totalbias = $fct_totalbias * 60;
// Make client timestamp
$fct_clienttimestamp = $fct_servertime + $fct_totalbias;
// Split time/date and format nicely
$fct_time = time();
$fct_year = strftime("%Y", $fct_clienttimestamp);
$fct_month = strftime("%m", $fct_clienttimestamp);
$fct_day = strftime("%d", $fct_clienttimestamp);
$fct_hour = strftime("%H", $fct_clienttimestamp);
$fct_minute = strftime("%M", $fct_clienttimestamp);
$fct_second = strftime("%S", $fct_clienttimestamp);
// Pad minutes and seconds with leading zero
$fct_minute = str_pad($fct_minute, 2, "0", STR_PAD_LEFT);
$fct_second = str_pad($fct_second, 2, "0", STR_PAD_LEFT);
// Print date and time
echo $fct_year."-".$fct_month."-".$fct_day."
".$fct_hour.":".$fct_minute.":".$fct_second;
// End of function
}
?>
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