I think you can try it like this;
if( $_POST['create'] == "channel" ) {
$nickname = $_POST['nickname'];
$channel = $_POST['channel'];
$password = $_POST['password'];
$descr = $_POST['descr'];
$chksum = md5("CHAN_REG:".$_POST["nickname"]." ".$_POST["channel"]." ".$_POST["password"]." ".$_POST["descr"].":".time().":supernova");
$cmd = "CHAN_REG";
$sqlcmd_checksum_salt = "supernova";
$params = "$nickname $channel $password $descr";
$tstamp = time();
$sql = "INSERT INTO database (cmd, params, tstamp, chksum, status) VALUES('$cmd','$nickname $channel $password $descr', '$tstamp', '$chksum', '0')";
.....
}