Iíve written code (below) of which receives posted fields data on to the acknowledgement page (Subscribe page > Acknowledge page), however the code is not working as expected so Iíve removed the other code (mainly the sanitizing of user input) and left the code were the users input is checked for empty spaces. This still isnít working...Iím a rooky, so any help is much appreciated

PHP Code:
if($_POST['username'] === "" ||$_POST['userfirstname']=== ""|| $_POST['usersecondname']=== ""||$_POST['useremail']=== ""||$_POST['userpassword']=== ""||
$_POST['userpasswordr']=== "")
$arr_fields = array("$_POST['username']""$_POST['userfirstname']""$_POST['usersecondname']""$_POST['useremail']",
$arr_fields as $arr_field)
$arr_field == "")
$arr_field "missing";
$var_username=            $_POST['username'];
$var_userfirstname=        $_POST['userfirstname'];
$var_usersecondname=        $_POST['usersecondname'];
$var_useremail=            $_POST['useremail'];
$var_userpassword=        $_POST['userpassword'];
$var_userpassword_repeat=     $_POST['userpasswordr'];
$arr_fields_processed = array("$var_username""$var_userfirstname""$var_usersecondname""$var_useremail",
header ("location: subscribe.php?arr_fields_processed");
     } else 

//sanitize code...