Why Don't PHP and JavaScript's Timestamps Match

Why don't PHP and Javascript's timestamps match?

JavaScript uses milliseconds as a timestamp, whereas PHP uses seconds. As a result, you get very different dates, as it is off by a factor 1000.

So remove three zeroes at the PHP side:

echo date('Y-m-d H:i:s', 1313690400);

Using PHP to Match a Javascript Timestamp

If you don't need (millisecond) presision, then just divide & Math.floor the javascript's function. So:

time();

and

Math.floor((new Date).getTime()/1000)

should return the same value at the same time.

unable to get date and time from timestamp in php?

Looks like you've got milliseconds in that timestamp. Try this:

$timestamp = 1483625713000 / 1000;
$date = date('d-m-Y', $timestamp);
$time = date('Gi.s', $timestamp);

var_dump($date);
var_dump($time);

Outputs

string(10) "05-01-2017"
string(7) "1415.13"

What is the difference between client-side and server-side programming?

Your code is split into two entirely separate parts, the server side and the client side.

                    |
               ---------->
              HTTP request
                    |
+--------------+    |    +--------------+
|              |    |    |              |
|    browser   |    |    |  web  server |
| (JavaScript) |    |    |  (PHP etc.)  |
|              |    |    |              |
+--------------+    |    +--------------+
                    |
  client side       |      server side
                    |
               <----------
          HTML, CSS, JavaScript
                    |

The two sides communicate via HTTP requests and responses. PHP is executed on the server and outputs some HTML and maybe JavaScript code which is sent as response to the client where the HTML is interpreted and the JavaScript is executed. Once PHP has finished outputting the response, the script ends and nothing will happen on the server until a new HTTP request comes in.

The example code executes like this:

<script type="text/javascript">
    var foo = 'bar';
    <?php
        file_put_contents('foo.txt', ' + foo + ');
    ?>

    var baz = <?php echo 42; ?>;
    alert(baz);
</script>

Step 1, PHP executes all code between <?php ?> tags. The result is this:

<script type="text/javascript">
    var foo = 'bar';

    var baz = 42;
    alert(baz);
</script>

The file_put_contents call did not result in anything, it just wrote " + foo + " into a file. The <?php echo 42; ?> call resulted in the output "42", which is now in the spot where that code used to be.

This resulting HTML/JavaScript code is now sent to the client, where it gets evaluated. The alert call works, while the foo variable is not used anywhere.

All PHP code is executed on the server before the client even starts executing any of the JavaScript. There's no PHP code left in the response that JavaScript could interact with.

To call some PHP code, the client will have to send a new HTTP request to the server. This can happen using one of three possible methods:

1. A link, which causes the browser to load a new page.
2. A form submission, which submits data to the server and loads a new page.
3. An AJAX request, which is a Javascript technique to make a regular HTTP request to the server (like 1. and 2. will), but without leaving the current page.

Here's a question outlining these method in greater detail

You can also use JavaScript to make the browser open a new page using window.location or submit a form, emulating possibilities 1. and 2.

JavaScript to PHP timestamp failing, adds about a month and a half to the time

That's because in Javascript's Date objects the month range is 0-11, not 1-12. That's for the "month" part. Try this:

var mn = j('#time_month :selected').val() - 1; //month

Or better, generate the <option>s with values ranging from 0 to 11.

Plus, this statement:

hr = j('#time_hour :selected').val()+12;

Remember that j('#time_hour :selected').val() is a string, not a number, so you have to convert it before adding 12, or else you'd get something like "0412". You're creating a date with the hour count set to 412, i.e. 17 days and 4 hours. And 17 days are addes to the day count.

Fix it like this:

hr = +j('#time_hour :selected').val() + 12;

I used the plus unary operator.

(P.S.: there's a lot of room to improve your code, starting with readability and jQuery object caching. Take some time improving your Javascript coding skills before getting used to some bad practices.)

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