php Only variables should be passed by reference

[Moorcam]

Hi guys,

I have the following code, which does work. The two problematic parts are pickup_location and drop_location. When I click Save the data is saved to the database and those two are saved to an array with multiple locations.

However, opening err_log, I get the following for each one:

Only variables should be passed by reference

<?php
// Include Header file which contains required credentials
include_once('includes/header.php');

// Initialize variables
$charterData = [
    'chtr_name' => '',
    'chtr_description' => '',
    'start_date' => '',
    'end_date' => '',
    'depot_start' => '',
    'depot_finish' => '',
    'driver' => '',
    'fleet_number' => '',
    'updated_by' => '',
    'customer_name' => '',
    'pickup_location' => [],
    'drop_location' => [],
    'pickup_time' => '',
    'return_time' => ''
];

try {
    // Fetch current charter details
    $charterId = (int)$_GET['chtr_id']; // Assuming the charter ID is passed via the URL
    $fetchStmt = $conn->prepare("SELECT chtr_name, chtr_description, start_date, end_date, depot_start, depot_finish, driver, fleet_number, updated_by, customer_name, pickup_location, drop_location, pickup_time, return_time FROM charters WHERE chtr_id = ?");
    $fetchStmt->bind_param("i", $charterId);
    $fetchStmt->execute();
// Initialize variables
$pickupLocations = null; // or an appropriate default value
$dropLocations = null;   // or an appropriate default value

$fetchStmt->bind_result(
    $charterData['chtr_name'],
    $charterData['chtr_description'],
    $charterData['start_date'],
    $charterData['end_date'],
    $charterData['depot_start'],
    $charterData['depot_finish'],
    $charterData['driver'],
    $charterData['fleet_number'],
    $charterData['updated_by'],
    $charterData['customer_name'],
    $pickupLocations, // Now properly initialized
    $dropLocations,    // Now properly initialized
    $charterData['pickup_time'],
    $charterData['return_time']
);

    $fetchStmt->fetch();
    $fetchStmt->close();

    // Convert pickup and drop locations from JSON to array
    $charterData['pickup_location'] = json_decode($pickupLocations, true) ?: [];
    $charterData['drop_location'] = json_decode($dropLocations, true) ?: [];

    // Check if the form is submitted
    if ($_SERVER["REQUEST_METHOD"] === "POST") {
        // User data
        foreach ($charterData as $key => $value) {
            if ($key === 'pickup_location' || $key === 'drop_location') {
                $charterData[$key] = array_filter(array_map('htmlspecialchars', $_POST[$key] ?? []));
            } else {
                $charterData[$key] = htmlspecialchars(trim($_POST[$key] ?? ''));
            }
        }

        // Prepare an SQL statement for updating the charter
        $stmt = $conn->prepare("UPDATE charters SET chtr_name = ?, chtr_description = ?, start_date = ?, end_date = ?, depot_start = ?, depot_finish = ?, driver = ?, fleet_number = ?, updated_by = ?, customer_name = ?, pickup_location = ?, drop_location = ?, pickup_time = ?, return_time = ? WHERE chtr_id = ?");
        
        // Bind parameters
        $stmt->bind_param("ssssssssssssssi", 
            $charterData['chtr_name'], 
            $charterData['chtr_description'], 
            $charterData['start_date'], 
            $charterData['end_date'], 
            $charterData['depot_start'], 
            $charterData['depot_finish'], 
            $charterData['driver'], 
            $charterData['fleet_number'], 
            $charterData['updated_by'], 
            $charterData['customer_name'], 
            json_encode($charterData['pickup_location']), 
            json_encode($charterData['drop_location']), 
            $charterData['pickup_time'], 
            $charterData['return_time'], 
            $charterId
        );

        // Execute the statement
        if (!$stmt->execute()) {
            throw new Exception("Error: " . $stmt->error);
        }
        echo '<script type="text/javascript">
        Swal.fire({
          icon: "success",
          title: "Great Job!",
          text: "Be proud! Charter has been updated successfully!",
          showConfirmButton: false,
          timer: 2500,
          footer: "Powered by NerfCMS"
        });
        </script>';
    }
} catch (Exception $e) {
    $ErrMsg = $e->getMessage();
}
?>

Can anyone please guide me in the right direction?

[Moorcam]

Ok,

After more research the issue was with these two lines:

    $pickupLocations, // Now properly initialized
    $dropLocations,    // Now properly initialized

These two variables are connected to a json_encode function. And, since json_encode returns a value rather than a variable, it cannot be passed by reference.

So, the fix was to predefine the json_encode and pass them then into the bind as follows:

// Prepare JSON encoded variables
$pickupLocation = json_encode($charterData['pickup_location']);
$dropLocation = json_encode($charterData['drop_location']);

// Bind parameters
$stmt->bind_param("ssssssssssssssi", 
    $charterData['chtr_name'], 
    $charterData['chtr_description'], 
    $charterData['start_date'], 
    $charterData['end_date'], 
    $charterData['depot_start'], 
    $charterData['depot_finish'], 
    $charterData['driver'], 
    $charterData['fleet_number'], 
    $charterData['updated_by'], 
    $charterData['customer_name'], 
    $pickupLocation, 
    $dropLocation, 
    $charterData['pickup_time'], 
    $charterData['return_time'], 
    $charterId
);

Hope this may help others in the future.

Edited 4 hours ago by Moorcam