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: 
You can include the browser in the sequence diagram but you should not include UI details. You should just have the requests that can be initiated via the browser. This diagram is a good example:

<http://click.apache.org/docs/user-guide/htmlsingle/images/ajax/ajax-request-sequence-diagram.png>
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)