Calculating Vat Rates Based on some variables - php

Question

The following function is working up to a point where I have to calculate the $vatamount based on some rules.
Ive got all my POST content from a script that fires my ajax request (code below is the code from the ajax URL).
The rules are - If the $bookingtype value is a "Corporate" booking or a "Groups" booking then the vat rate is calculated over the length of stay. 20% for anything up to 28 nights and 4% for anything over 28 nights.
However, if the $bookingtype value is a "Leisure" booking then the vat rate is 20% regardless of the length of stay.
I've got the function to return the right VAT percentage. But that last if statement just isn't working for me. Im a php newbish and i think I've done well to get this far with it. Just need some assistance completing this function. I think I've screwed my syntax in there somewhere lol
The last echo should echo the calculated vat amount.
Thanks in advance.
function implement_ajax_vat() {
if(isset($_POST['arrivaldate']))
{
//get the start and end dates
$startdate = ($_POST['arrivaldate']);
$enddate = ($_POST['leavingdate']);
$datetime1 = new DateTime($startdate);
$datetime2 = new DateTime($enddate);
$interval = $datetime1->diff($datetime2);
$numberofnights = $interval->format('%a nights');
//calculatge the VAT amount
$bookingtype = ($_POST['bookingtype']);
$rentalprice = ($_POST['rentalprice']);
//check numbr of nights
if($numberofnights >= 29){
$vatrate = "4";
} elseif ($numberofnights <= 28) {
$vatrate = "20";
}
//get the booking type and check if its a variable rate
if(($bookingtype = 'Corporate') || ($bookingtype = 'Groups')){
$vatamount = ($rentalprice / 100) * $vatrate;
} elseif ($bookingtype = 'Leisure') {
$vatamount = "20";
}
echo $vatamount;
die();
}
}

Answer 1

You are assigning values instead of comparing: use double equals sign ==:
if($bookingtype == 'Corporate' || $bookingtype == 'Groups'){
^ ^
$vatamount = ($rentalprice / 100) * $vatrate;
} elseif ($bookingtype == 'Leisure') {
^
$vatamount = 20;
}
That's why first statement yields true as you assign and return there non-empty string, so you never go to elseif section.