how to call wordpress function on click in a custom plugin - php

Question

I've been having a go at creating a custom plugin (simplified code below).
I have my plugin file (counter.php) which has 2 function in it called
displayCount() {
// output count and a link to add 1
echo 'Add One';
}
AND
addOne() {
$count = $count + 1;
}
My question is what to I replace XXX with or how do I call addOne function from my post page?

Answer 1

You're attempting to modify the PHP on the user's end, but unfortunately all PHP has already run when the user is able to click the link. PHP is a server side language, Javascript is a client-side language. In order to pass data back and forth, you'll need Ajax.
However, it looks like what you're trying to do could be done with pure Javascript. Something like this:
<div id="counter"></div>
Add one
<!-- INCLUDE JQUERY HERE (or elsewhere on page, perhaps head) -->
<script type="text/javascript">
// Create global JS var to track the count.
var counter = 0;
// On document ready we need to assign a click event.
// We use document ready to be sure that we select all
// initial elements when the page is loaded.
jQuery('document').ready(function()
{
// On counter-add click...
jQuery('.counter-add').click(function()
{
// Increment counter
counter++;
// Output counter value
jQuery('#counter').text(counter);
});
});
</script>
Here is a working JSBIN copy.