Update PHP variable with js .innerHTML [duplicate] - php

Question

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Closed 10 years ago.
Possible Duplicate:
How do I programatically set the value of a select box element using javascript?
I'm trying to update a table with the results of a query when a select option has changed. The following test code works fine. But when I try to update the query, it doesn't work. I'm guessing it has to do with the 'echo', but I cant get figure it out. Thanks.
<script type="text/javascript">
function ChangeText(value)
{
document.getElementById("p1").innerHTML=value;
}
</script>
<select onchange="ChangeText(value)">
<option value="ONE">one</option>
<option value="TWO">two</option>
<option value="THREE">three</option>
<option value="FOUR">four</option>
</select>
<?php
$variable1 = '<p id="p1">place holder</p>';
echo $variable1;
?>
what doesn't work:
document.getElementById("country").innerHTML=value;
$country = '<p id="country">United States</p>'
$result = mysql_query("SELECT * FROM statistics WHERE (Country='$country')");
The result of that is a blank table when the page loads, I would have expected 'United States' to be the default value. And when I select something from the pulldown, it does nothing.

Answer 1

PHP is executed on the server-side, before the user ever sees the page. So once the user is looking at the page, PHP is done executing.
So you can't "update a PHP variable with Javascript, because Javascript runs on the client-side, which happens after PHP has completely finished executing.
You should look into AJAX.

Answer 2

I think you have some confusion about how server-side scripting vs javascripting works. PHP code does not run on the client side. PHP code is executed by your server, and the results (everything echoed + HTML markup) is sent to the client's browser. If you want to dynamically update a page you would have to use a form and reload the page, or use AJAX.