Updating Time in Local Storage

Question

I am trying to connect to the server every minute and pass in the variable of the current time, which would be the lastUpdate. On the server side php file, I plan to compare the passed in time variable with a TIMESTAMP in the database rows; much like if (time1-time2 > certain value)... So far the javascript code is:

var time;
var timer_is_on = 0;
localStorage.lastUpdate = 0;
localStorage.numUpdates = 0;

function timedCount()
{
    localStorage.lastUpdate = new Date();
    //connect to server
    contactServer(localStorage.lastUpdate);
    currentCount=currentCount+1;
    time=setTimeout("timedCount()",60000);
}

My question is whether I am doing this correctly. I am declaring localStorage.lastUpdate as new Date() and I'm not sure whether this is correct? I have tried the loop and every minute lastUpdate seems to be the same date and time.

My last question is whether I can actually compare the two time formats from javascript and php. In the SQL timestamp, the format is 2012-03-20 11:14:40 while the date format from the javascript new Date() is Tue Mar 20 2012 12:32:44 GMT-0400 (Eastern Daylight Time) .

Any information would be helpful, thanks!

Answer 1

Be careful when you use time. Your server time may be different from your client time. The best for you is to store the date of the last request in $_SESSION['last']. With this solution, all your problems are not anymore. Your PHP set the date, so it is the same reference, and it's in a good format.

Just keep your timeout on the client side:-)

Answer 2

Use new Date().getTime() to return a UNIX timestamp; that is, the number of seconds since Jan 1st, 1970. This makes it much easier to compare with other times.

localStorage.lastUpdate = new Date().getTime();

Will return something like this: 1332266002.

The PHP equivalent is simply time() .

And to convert that UNIX timestmap into a MySQL TIMESTAMP , use MySQL's FROM_UNIXTIME function.