if(!empty(isset($_POST["SHOWSCHEDULE_SHOWTYPE"]))){
    $DATA["SHOWSCHEDULE_SHOWTYPE"] = $_POST["SHOWSCHEDULE_SHOWTYPE"];
}

if(!empty(isset($_POST["SHOWSCHEDULE_SHOWTITLE"]))){
    $DATA["SHOWSCHEDULE_SHOWTITLE"] = $_POST["SHOWSCHEDULE_SHOWTITLE"];
}

if(empty($DATA)){
    //do something
}else{
    //do something else
}

if(!empty($_POST['var1']) && !empty($_POST['var2']) && !empty($_POST['var3']) && !empty($_POST['var4'])):
/*and then assign all the POST values to a $DATA array as you want.*/
$DATA['var1'] = $_POST['var1'];
$DATA['var2'] = $_POST['var2'];/* and so on..*/
endif;

if(!empty(isset($_POST["SHOWSCHEDULE_SHOWTYPE"])) && !empty(isset($_POST["SHOWSCHEDULE_SHOWTITLE"]))){

    $DATA["SHOWSCHEDULE_SHOWTYPE"] = $_POST["SHOWSCHEDULE_SHOWTYPE"];
    $DATA["SHOWSCHEDULE_SHOWTITLE"] = $_POST["SHOWSCHEDULE_SHOWTITLE"];

}else{
    //do nothing
}