Question: I recently wrote a C program that is supposed to run in a Linux environment as follows;

```
#include <stdio.h>
#include <stdlib.h>

void main()
{
    system("notify-send -u normal -t 200 'You Have received a new message'");
    system("cvlc /home/ashenafis/Music/BabyMessage.mp3");
    return 0;
}

```

Compiled it and saved the executable in "/usr/sbin/play".

When I run it from the terminal it works fine, however it does not work when I try to run it from a PHP script using

```
<?php exec("/usr/sbin/play"); ?>

```

Is there something I am missing? Please help.

Answer: 
UML sequence diagrams are used to represent or model the flow of messages, events and actions between the objects or components of a system. For this login should be the component of the system (as a class) rather then a page. Object will be ur user who tries to login. i would recommend you to go through this link for sequence diagram intro -
[intro to sequence diagram](http://www.sequencediagrameditor.com/uml/sequence-diagram.htm) 

and for the login sequence diagram

[sequence diagram of login page](http://people.cis.ksu.edu/~reshma/798_SequenceDiagram.htm)
In my view you are trying to show the sequence of interactions between objects for *purchase of a product*.

In this case the web page or the view **should not be in the diagram**. The page/view is a means of interaction with the user and might be displayed as an external call to a *endpoint* which will actually deal with a purchase request. So, probably the first/left-most *object* in your sequence diagram will be the controller/endpoint which receives this call.