Implementing Server-Side Arithmetic

To build a functional calculator interface, the backend must retrieve input parameters from the submision method. Using a switch structure ensures clean branching for multiple operations while validating inputs to prevent runtime errors.

<?php
$result = null;

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $num1 = floatval($_POST['operand1']);
    $num2 = floatval($_POST['operand2']);
    $action = $_POST['math_type'];

    switch ($action) {
        case '+':
            $result = $num1 + $num2;
            break;
        case '-':
            $result = $num1 - $num2;
            break;
        case '*':
            $result = $num1 * $num2;
            break;
        case '/':
            $result = ($num2 !== 0) ? $num1 / $num2 : 'Invalid Operation';
            break;
    }
}
?>

<form method="post">
    <input type="text" name="operand1"><br>
    Select Operator:
    <label><input type="radio" name="math_type" value="+">+</label>
    <label><input type="radio" name="math_type" value="-">-</label>
    <label><input type="radio" name="math_type" value="*">*</label>
    <label><input type="radio" name="math_type" value="/">/</label><br>
    <input type="text" name="operand2"><br>
    <button type="submit">Calculate</button>
</form>

<p>Final Output: <?php echo isset($result) ? htmlspecialchars($result) : ''; ?></p>

Filtering Numbers by Divisibility Criteria

This exercise requires identifying integers with in a specific range that satisfy multiple mathematical conditions simultaneously. Optimizing the conditional checks reduces computational overhead during iteration.

<?php
for ($i = 0; $i < 100; $i++) {
    $remainder = $i % 3;
    $lastDigit = $i % 10;

    if ($remainder === 0 && $lastDigit === 6) {
        echo $i . " ";
    }
}
?>

Resolving Remainder Constraints

Solving problems involving modular arithmetic often involves iterating through a candidate range until the congruence equations are satisfied. The logic below finds the unique integer between 100 and 199 meeting the specified grouping requirements.

<?php
for ($total = 100; $total < 200; $total++) {
    if ($total % 3 === 1 && $total % 4 === 2 && $total % 5 === 3) {
        echo "Solution found: " . $total . "\n";
    }
}
?>

Financial Deduction Simulation

This simulation demonstrates state management in loops, specifically tracking currency decay based on varible thresholds. The loop terminates once the funds drop below the required threshold for transaction survival.

<?php
$cash = 100000;
$passCount = 0;

while ($cash > 0) {
    $passCount++;
    
    if ($cash > 50000) {
        $deduction = $cash * 0.05;
        $cash -= $deduction;
    } else {
        $cash -= 5000;
    }
}

echo "Total crossings possible: " . $passCount;
?>