A "Locksmith Calculator" could include various features and fields to make it more comprehensive and useful for a locksmith or a customer estimating service costs. Here's a breakdown of what I would include:
1. Basic Input Fields:
  - Trip Fee: The base fee for the locksmith to travel to the location.
  - Service Fee: The fee for the specific locksmith service provided (e.g., unlocking a door, changing a lock).
  - Fees Per Mile: The charge per mile traveled.
  - Miles Traveled: The distance the locksmith traveled to reach the customer.
2. Additional Input Fields:
  - After-Hours Fee: Extra charges if the service is provided outside regular business hours (e.g., late night, weekends).
  - Emergency Service Fee: Additional fees for emergency or urgent service requests.
  - Material Costs: Costs for materials like new locks, keys, or other hardware.
  - Discounts: Any applicable discounts (e.g., senior citizen discount, promotional discounts).
  - Tax Rate: Applicable sales tax for the service.
3. Calculation Features:
  - Mileage Fee Calculation: Automatically calculate the mileage fee based on the miles traveled and the per-mile rate.
  - Total Cost Calculation: Sum of all applicable fees and taxes.
  - Itemized Breakdown: Display an itemized breakdown of each component of the total cost.
4. Output Display:
  - Trip Fee
  - Service Fee
  - Mileage Fee
  - After-Hours Fee (if applicable)
  - Emergency Service Fee (if applicable)
  - Material Costs (if applicable)
  - Discounts (if any)
  - Tax Amount
  - Total Cost
 5. User-Friendly Features:
  - Responsive Design: Ensure the calculator works well on both desktop and mobile devices.
  - Clear Error Messages: Validate user input (e.g., ensure numeric values where needed) and display clear error messages for invalid inputs.
  - Customizable Options: Allow the locksmith to input their specific rates and fees, which can be saved for future use.
6. Advanced Features (Optional):
  - PDF/Email Invoice Generation: Generate an invoice based on the calculated total that can be saved as a PDF or emailed directly to the customer.
  - Customer Information: Input fields for customer details (name, address, contact info) to include on the invoice.
  - Multiple Services: Ability to add multiple services to the same calculation (e.g., unlocking a car + changing a house lock).
  - Historical Data: Save previous calculations for future reference or comparison.
These features would make the Locksmith Calculator a robust tool for both locksmiths and their customers, providing accurate cost estimates and easy-to-understand breakdowns of charges.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Locksmith Calculator</title>
</head>
<body>
<h1>Locksmith Calculator</h1>
<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
$tripFee = floatval($_POST['tripFee']);
$serviceFee = floatval($_POST['serviceFee']);
$feesPerMile = floatval($_POST['feesPerMile']);
$miles = floatval($_POST['miles']);
$afterHoursFee = floatval($_POST['afterHoursFee']);
$emergencyServiceFee = floatval($_POST['emergencyServiceFee']);
$materialCosts = floatval($_POST['materialCosts']);
$discount = floatval($_POST['discount']);
$taxRate = floatval($_POST['taxRate']);
// Calculate the fees
$mileageFee = $feesPerMile * $miles;
$subtotal = $tripFee + $serviceFee + $mileageFee + $afterHoursFee + $emergencyServiceFee + $materialCosts;
$totalCostBeforeDiscount = $subtotal - $discount;
$taxAmount = $totalCostBeforeDiscount * ($taxRate / 100);
$totalCost = $totalCostBeforeDiscount + $taxAmount;
// Display the results
echo "<h2>Calculation Results:</h2>";
echo "<p>Trip Fee: $" . number_format($tripFee, 2) . "</p>";
echo "<p>Service Fee: $" . number_format($serviceFee, 2) . "</p>";
echo "<p>Mileage Fee: $" . number_format($mileageFee, 2) . "</p>";
echo "<p>After-Hours Fee: $" . number_format($afterHoursFee, 2) . "</p>";
echo "<p>Emergency Service Fee: $" . number_format($emergencyServiceFee, 2) . "</p>";
echo "<p>Material Costs: $" . number_format($materialCosts, 2) . "</p>";
echo "<p>Subtotal: $" . number_format($subtotal, 2) . "</p>";
echo "<p>Discount: -$" . number_format($discount, 2) . "</p>";
echo "<p>Tax Amount: $" . number_format($taxAmount, 2) . "</p>";
echo "<p>Total Cost: $" . number_format($totalCost, 2) . "</p>";
}
?>
<h2>Enter Locksmith Fees:</h2>
<form method="post" action="">
<label for="tripFee">Trip Fee ($):</label><br>
<input type="text" id="tripFee" name="tripFee" required><br><br>
<label for="serviceFee">Service Fee ($):</label><br>
<input type="text" id="serviceFee" name="serviceFee" required><br><br>
<label for="feesPerMile">Fees Per Mile ($):</label><br>
<input type="text" id="feesPerMile" name="feesPerMile" required><br><br>
<label for="miles">Miles Traveled:</label><br>
<input type="text" id="miles" name="miles" required><br><br>
<label for="afterHoursFee">After-Hours Fee ($):</label><br>
<input type="text" id="afterHoursFee" name="afterHoursFee"><br><br>
<label for="emergencyServiceFee">Emergency Service Fee ($):</label><br>
<input type="text" id="emergencyServiceFee" name="emergencyServiceFee"><br><br>
<label for="materialCosts">Material Costs ($):</label><br>
<input type="text" id="materialCosts" name="materialCosts"><br><br>
<label for="discount">Discount ($):</label><br>
<input type="text" id="discount" name="discount"><br><br>
<label for="taxRate">Tax Rate (%):</label><br>
<input type="text" id="taxRate" name="taxRate"><br><br>
<input type="submit" value="Calculate">
</form>
</body>
</html>
How It Works:
1. Form Submission**: The user inputs the Trip Fee, Service Fee, Fees Per Mile, Miles Traveled, After-Hours Fee, Emergency Service Fee, Material Costs, Discounts, and Tax Rate.
2. Calculations**:
  - Mileage Fee = Fees Per Mile × Miles Traveled
  - Subtotal = Trip Fee + Service Fee + Mileage Fee + After-Hours Fee + Emergency Service Fee + Material Costs
  - Total Cost Before Discount = Subtotal - Discount
  - Tax Amount = Total Cost Before Discount × (Tax Rate / 100)
  - Total Cost = Total Cost Before Discount + Tax Amount
3. Results Display: The script displays an itemized breakdown of each fee and the total cost.
This enhanced calculator provides a more detailed estimate and allows for a wide range of scenarios to be covered, making it a versatile tool for both locksmiths and customers.