calling a different classes function via a form php - php

Question

We are toying about with the Open Source Flamer app. We noticed that they are able to call a function in a separate class located in a different PHP file via a form POST request. Here is an example of how they do it:
<div id="upldate_location_service" class="div_service">
<form action="process.php/upDetails" method="post">
<h3>Update location :</h3>
<div class="form_row">
<div class="form_label">Session Token *: </div>
<div class="form_field"><input type="text" name="ent_sess_token" />name= "ent_sess_token"</div>
</div>
<div class="form_row">
<div class="form_label"> </div>
<div class="form_field"><input type="submit" name="ent_submit" value="Submit" /></div>
</div>
</form>
</div>
The function they are trying to access is UpdateLocation in the file Process.php. We have tried to recreate this process but it wont work. We can echo outside of our class, but for some reason we cant access or run any content in our process.php function.
Here is a copy of our process document:
class LegitAPI Extends API{
public function upDetails($args)
{
echo "Hello World";
}
}
Theoretically, when submitting the form on the index page, it should load process.php and then the method upDetails in the LegitAPI Class and display hello world. However, a blank page is instead being displayed.
Any ideas?