<?php
function calculateDSCR($interest_rate, $fixed_or_arm, $io_term, $loan_amount, $taxes, $insurance, $hoa, $gross_rent) {
// Convert annual interest rate to a monthly rate
$monthly_interest_rate = $interest_rate / 100 / 12;
$io_months = 0; // Default

// Determine the number of months based on IO term description
switch ($io_term) {
case '18 Month Interest Only No Impounds':
$io_months = 18;
break;
case '24 Month Interest Only':
$io_months = 24;
break;
case '36 Month Interest Only':
$io_months = 36;
break;
case '30 Year Due In 5 Year PITI':
$io_months = 60; // Assuming this term means a 30-year loan with something specific happening in the first 5 years
break;
}

// Calculate monthly payment
if ($io_months > 0) {
$monthly_payment = $loan_amount * $monthly_interest_rate; // Interest-only payment
} else {
$n = 360; // Total number of payments (30 years x 12 months)
$monthly_payment = $loan_amount * ($monthly_interest_rate * pow(1 + $monthly_interest_rate, $n)) / (pow(1 + $monthly_interest_rate, $n) - 1);
}

// Calculate PITIA payment
$pitia_payment = $monthly_payment + $taxes + $insurance + $hoa;

// Calculate DSCR
$dscr = $gross_rent / $pitia_payment;

return $dscr;
}

// Check if the form has been submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
$interest_rate = floatval($_POST['interest_rate']);
$fixed_or_arm = $_POST['fixed_or_arm'];
$io_term = $_POST['io_term'];
$loan_amount = floatval($_POST['loan_amount']);
$taxes = floatval($_POST['taxes']);
$insurance = floatval($_POST['insurance']);
$hoa = floatval($_POST['hoa']);
$gross_rent = floatval($_POST['gross_rent']);

$dscr = calculateDSCR($interest_rate, $fixed_or_arm, $io_term, $loan_amount, $taxes, $insurance, $hoa, $gross_rent);

echo "DSCR: " . number_format($dscr, 3) . "<br>";
echo $dscr >= 1.0 ? "Loan qualifies for DSCR." : "Loan does not qualify for DSCR.";
}
?>

<!-- HTML form for input -->
<form method="post">
Interest Rate (%): <input type="text" name="interest_rate"><br>
Fix or ARM (Enter 'Fix' or 'ARM'): <input type="text" name="fixed_or_arm"><br>
IO Term: <select name="io_term">
<option value="0">Select IO Term</option>
<option value="18 Month Interest Only No Impounds">18 Month Interest Only No Impounds</option>
<option value="24 Month Interest Only">24 Month Interest Only</option>
<option value="36 Month Interest Only">36 Month Interest Only</option>
<option value="30 Year Due In 5 Year PITI">30 Year Due In 5 Year PITI</option>
</select><br>
Loan Amount ($): <input type="text" name="loan_amount"><br>
Taxes ($): <input type="text" name="taxes"><br>
Insurance ($): <input type="text" name="insurance"><br>
HOA ($, enter 0 if not applicable): <input type="text" name="hoa"><br>
Gross Rent ($): <input type="text" name="gross_rent"><br>
<input type="submit" value="Calculate DSCR">
</form>