Useing Php functions

Commissar

I'm pretty much a novice at Php programming (My project team's regular Php programmer had to leave) and I'm struggeling to get a function to work.

"Fatal error: Call to undefined function: writefile()"

<?php
session_start();
.
.
.
function writeFile(){
$fileName = $HTTP_SESSION[exam];

$ourFileHandle = $fopen($fileName, "w");
$someData = "***".$HTTP_SESSION_VARS[exam]."***".$HTTP_SESSION_VARS["ex1"]."***".$HTTP_SESSION_VARS["ex2"]."***".$HTTP_SESSION_VARS["ex3"]."***";

fwrite($ourFileHandle, $someData );

fclose($ourFileHandle);
}
.
.
.
writeFile();
session_destroy();
}
}
?>
</body>
</html>


Can anybody give me any tips regarding this error message?
Are there limitations on where functions can be declared? Or could there be a proble with useing SESSION variables within the function?

As I said I know very little Php so any help would be appreciated.
Thanks.

edited to include code.

is_that_so

Please paste some code to show where your problem is. The error generally means it can't find it.

If it is a file you want to write to, use fwrite() . Also check out www.php.net for functions.

timeout

Are there any other functions in the same code?Do they execute ok?
Normally i'd define most of my functions in a sepearte file and just include them or if defining in the file would keep them at the top.
Should not be a problem using session variables within the function.
A call to an undefined function just means it doesn't know about the function, generally its a case of missing a ; or a }
I see you are missing "" here:

$HTTP_SESSION_VARS[exam]