ExpenseTable

<?php
function getMonths()
{
    $months = [];
    $months[] = "<th class='normalMontг'>January</th>";
    $months[] = "<th class='redMonth'>March</th>";
    $months[] = "<th class='redMonth'>October</th>";
    $months[] = "<th class='redMonth'>November</th>";

    return $months;
}
?>
<html>
<head>
    <title>Annual Expenses</title>
</head>
<body>
<form action="" method="post">
    <label for="years">Enter number of years:</label>
    <input type="text" name="years" id="years"/>
    <input type="submit" value="Show costs"/>
</form>
</body>
</html>
<?php if(isset($_POST['years']) && is_numeric($_POST['years'])): ?>
<table border="1">
    <tr>
        <th>Year</th>
        <?php foreach (getMonths() as $monthElement): ?>
            <?= $monthElement; ?>
        <?php endforeach; ?>
        <th>Total:</th>
    </tr>
    <?php for ($year = date("Y"); $year > (date("Y") - $_POST['years']); $year--): $sum = 0 ?>
    <tr>
        <td><?= $year; ?></td>
        <?php for ($i = 0; $i < count(getMonths()); $i++): $currentExpense = rand(0, 99) ?>
            <td><?= $currentExpense; ?></td>
        <?php $sum += $currentExpense; endfor; ?>
        <td><?= $sum; ?></td>
    <?php endfor; ?>
    </tr>
</table>
<?php endif; ?>