PHP session: two values are ALWAYS sent - php

Question

I'm pretty new to PHP but trying to find my way which has worked quite well up till now.
Problem is the following: I have a website with 2 links. Both should redirect to the same second website but depending on the link clicked, some values should change. I was trying to use a PHP session for this.
Here is the code up to now:
Link 1:
<a href="<? echo $link ?>" class="helsinki" onclick="<? $_SESSION['clicked']= "helsinki"; ?>"^^Helsinki^^</a>
Link 2:
^^Seattle^^
Now if I try to read which link was clicked on the next side like this:
<? if(isset($_SESSION['clicked']))
echo "clicked ". $_SESSION['clicked'];
?>
I always see "Seattle", Helsinki never appears although (I thought) I input Seattle if the Seattle link is clicked. Apparently it's not like that... Can anyone help me here?

Answer 1

This is because PHP code is server side, and thus executed at the time of the page request. So $_SESSION['clicked'] is set to helsinki then reset to seattle at the time your first page loads. You may want to use $_GET variables instead of $_SESSION variables.

Answer 2

Wait wait wait a second: PHP is "server-side", javascript is "client-side". That means you will ALWAYS execute PHP before javascript.
What you are trying to achieve can be simply done with a GET variable:
^^Seattle^^
^^Helsinki^^
And than in the second site you can get the value of our parameter:
$city = $_GET['city'];

Answer 3

Not sure if this is useful, but you could create a "redirector". It takes the user to a server side page that will redirect them to the final page and at the same time change the session.
The page:
...
...
The code for redirector.php:
<?php
session_start();
// determine where to redirect user (could be done with database or array of options)
switch ($_GET['link']) {
case 'helsinki':
header('Location: /link/to/helsinki');
break;
case 'seattle':
header('Location: /link/to/seattle');
break;
default:
return;
}
$_SESSION['clicked'] = $_GET['link'];

Answer 4

You're mixing up Javascript and PHP.
PHP is server side, that means that all PHP code is parsed and executed on the server side, and then is sent to the client.
So if you write
line #1: ^^Helsinki^^
and then
line #2: ^^Seattle^^
the value of $_SESSION['clicked'] is always first "Helsinki" (line #1), but then immediately overwritten by "Seattle" (on line #2).
In order to achieve what you want the script to achieve, is, for example, as follows:
^^Helsinki^^
^^Seattle^^
and then catch the sent variables from the PHP variable $_GET:
if (isset($_GET['location'])) {
if ($_GET['location'] == "helsinki") {
// Whatever
}
elseif ($_GET['location'] == "seattle") {
// You want
}
}

Answer 5

"^^Helsinki^^
"^^Seattle^^
and use $_GET['location'] at the other page to check weather it is helsinki or seattle.
$link should be the same for both links.
Also you can't mix PHP (server-side) with Javascript (client-side). Look it up for why that is.

Answer 6

You cannot write PHP code in the onclick event. If you want to do it like that, you should use Javascript/AJAX. Even if you do it like that, you won't still get the result as you desire, since AJAX request will delay some seconds.
I think the right way to do this kind of thing is like below:
Helsinki"
and this is the change_city.php:
<?php
$_SESSION["clicked"] = $_GET["city"];
?>
if you want to still use the $link, then you just put this above code top of your PHP file.