Get value from a javascript function in a php variable

Question

so I have this javascript function on my page which computes date. Now, I want to access the result thrown by the function in a php variable so that I can use that variable to insert value in a database. The function should be called on page load. I have been trying to get this done from past 4 hours but upto no solution, any suggestions and solutions are welcome.

My JS Code:-

<script language="JavaScript">
// function to calculate local time
// in a different city
// given the city's UTC offset
function calcTime(city, offset,selDate,selHours,selMinutes) {
//alert(selDate);
//alert(selHours);
//alert(selMinutes);
//alert(offset);
var str = selDate;
var res = str.split("/");
//07,26/2014
//0,1,2
var d = new Date(res[2], res[0], res[1], selHours, selMinutes, 0, 0);
 // create Date object for current location
 //alert(d);
 // var d = new Date();
 //alert(d);
 // convert to msec
 // add local time zone offset 
 // get UTC time in msec
 utc = d.getTime() + (d.getTimezoneOffset() * 60000);
 // create new Date object for different city
 // using supplied offset
 nd = new Date(utc + (3600000*offset));
 // return time as a string
 return nd.toLocaleString();
}
function testTime(){
var selDate = document.getElementById("datepicker").value;
var selHours = document.getElementById("hours").value;
var selMinutes = document.getElementById("minutes").value;
var selTimeZone = document.getElementById("timezone").value;
alert(selDate);
alert(selHours);
alert(selMinutes);
alert(selTimeZone);
}
</script>

• Sudhir Bastakoti: did you try using Ajax..!
• asprin: Look up Ajax. You'll get your answer
• user3369276: Yes, I read that using Ajax might help. But I haven;t used it before, and understanding the syntax was a bit tough. That's why I posted the question here.
• rlatief: You can't "get value from a javascript function directly to a php function" because JS is executed after all php stuff is done. You can however call php function, in another "file", by using ajax.
• rlatief: See here: api.jquery.com/jquery.get ... GET another file with the php function in it, pass whatever you want through query string :-) eg: $.get( "ajax/dowork.php?selected=" + selDate );

Answer 1

To allow your JavaScript to communicate with your PHP backend, you'll have to use Ajax. This allows you to send information to a PHP file.

For the sake of keeping it simple, I suggest you use jQuery, it has two useful methods you can use $.ajax and $.get

Your JavaScript could look something like this:

$(document).ready(function(){
 var timeToSend = calcTime(city, offset,selDate,selHours,selMinutes);
 //we are sending information to saveTimeToDB.php
 $.ajax('saveTimeToDB.php', {
 data: {time:timeToSend}//this is an object containing all the information you want to send 
 }).done(function(){
 //a function which gets called if the ajax call succeeded
 alert('the time has been saved');
 }).fail(function(){
 //a function which gets called if the ajax call failed
 alert('Uh-oh, something went wrong. We did not save the time');
 });
});

In the 'saveTimeToDB.php' file you can now access this variable with:

$time = $_GET['time'];

You should then be able to use this variable and insert it in your database.

Make sure to do many checks on this variable, to make sure you're not injecting anything malicious in to your DB.

Answer 2

Javascript and PHP do't have any interaction due to JS being client side and PHP being server side.

PHP will be executed before the JS.

So, what you can do is use a hidden field:

<input type="hidden" name="hid" id="date">

and the value of javascript variable in that:

document.getElementById('date').value=date; //whatever value you want to store

and then simply fetch the value of this field like you do normally with textboxes.

Or simply use AJAX to send data from client to server as others already said:

$.ajax({
 url: something.php // current page
 type: 'POST',
 data: {
 var1: 'date' // of if writing a JS variable remove the quotes.
 },
 success: function() {
 // whatever
 }
});

to call a function on page load write: <body onload="foo()">

• user3369276: Thank you for posting. But I'm not sure how your solution is gonna help my case.
• user63762453: You want the value returned by function calcTime?
• user63762453: see the edited answer, I think I earlier posted code for the reverse :D
• user3369276: Correct, and the function should be called on page load.
• user3369276: I can do that. But the problem is, the calculation needs to be done on the same page I need to do database insertion. Otherwise, I might be have brought the value forward from a form via a different page.

Answer 3

I'm not sure about the JS, but if the function is correct then try to write this before </script> of your posted code above, and open the file (from browser):

alert calcTime('city', 3,2,12,30);

If what's alerted is what you want, then:

$.get( "ajax/dowork.php?calculatedTime=" + calcTime('city', 3,2,12,30) );

... will call dowork.php (where you put DB insert codes in it, and you'll have $_GET['calculatedTime'] to insert).

• rlatief: forgot singlequote in 'city'
• user3369276: I need the the value on the same page. Because there are like 10 other fields which will be inserted to the DB.
• rlatief: pass that other 10 fields as well. If there're a lot you might want to use $.post eg: $.post( "test.php", { name: "John", time: "2pm" } ); --- the basic idea is, you can't use JS-generated value on a PHP function on the same page (because PHPs are done, before any JS is executed).