PHP Session Problem / Forms

[CCT.Darren]

I am very new to PHP comming from an ASP back ground, so what I like to know are the following if at all possible.

1: I have just writen a scrip that uses session versbles to maintain securaty, so people can't use the scrip for sending spam mail, my local PC witch is runing IIS and PHP5 runs the scrip Ok, comes up now and again with a silly session error whitch I not been able to fix, sea below

Notice: A session had already been started - ignoring session_start() in C:\web sites\passion8\sf\sendm.php on line 6

Whitch I put the following code in to try and fix some times it works other times it dose not!

//Start the session for securaty!
if (!isset($_SESSION['domail'])) {
session_cache_limiter('private');
session_cache_expire(5);
session_start();
$_SESSION['domail'] =1;
}

2:
I assume that on there servcer to use session verables I need this function turn on, the server running linux and apachi 2.

any one>