source: PayFines.php

<?php
session_start();
require './connect.php';

// Check if user is logged in
if (!isset($_SESSION['userid'])) {
    echo json_encode(['success' => false, 'message' => 'User not logged in']);
    exit;
}

try {
    // Begin transaction
    $conn->beginTransaction();

    // Get all unpaid fines for the current user
    $getFines = "SELECT fineid, fineamount 
                 FROM fine 
                 WHERE status = 'Unpaid' 
                 AND loanid IN (SELECT loanid FROM loan WHERE memberid = :userid)";
    $stmt = $conn->prepare($getFines);
    $stmt->bindParam(':userid', $_SESSION['userid'], PDO::PARAM_INT);
    $stmt->execute();
    $unpaidFines = $stmt->fetchAll(PDO::FETCH_ASSOC);

    if (empty($unpaidFines)) {
        throw new Exception('No unpaid fines found');
    }

    // Process each unpaid fine
    foreach ($unpaidFines as $fine) {
        // Insert payment record
        $insertPayment = "INSERT INTO finepayment (paymentdate, paymentamount, fineid) 
                         VALUES (CURRENT_TIMESTAMP, :amount, :fineid)";
        $stmt = $conn->prepare($insertPayment);
        $stmt->bindParam(':amount', $fine['fineamount'], PDO::PARAM_STR);
        $stmt->bindParam(':fineid', $fine['fineid'], PDO::PARAM_INT);
        $stmt->execute();

        // Update fine status
        $updateFine = "UPDATE fine 
                      SET status = 'Paid', 
                          finedate = CURRENT_TIMESTAMP 
                      WHERE fineid = :fineid";
        $stmt = $conn->prepare($updateFine);
        $stmt->bindParam(':fineid', $fine['fineid'], PDO::PARAM_INT);
        $stmt->execute();
    }

    // Commit transaction
    $conn->commit();

    echo json_encode([
        'success' => true,
        'message' => 'All fines paid successfully'
    ]);

} catch (Exception $e) {
    // Rollback transaction on error
    $conn->rollBack();
    echo json_encode([
        'success' => false,
        'message' => $e->getMessage()
    ]);
}
?>