Advanced_Customer.php

<?php

$errors = [];
$data = [];

$string = "";

$Fname = $_POST['Fname'];
$Lname = $_POST['Lname'];
$email = $_POST['email'];
$phone = $_POST['phone'];
$street = $_POST['street'];
$city = $_POST['city'];
$country = $_POST['country'];

if (!empty($Fname)) {

    if ($string != "") {
        $string = $string . "AND  ";
    }
    $string = $string . "first_name= '" . $Fname . "'";

}

if (!empty($Lname)) {

    if ($string != "") {
        $string = $string . "AND  ";
    }
    $string = $string . "last_name= '" . $Lname . "'";

}

if (!empty($email)) {

    if ($string != "") {
        $string = $string . "AND  ";
    }
    $string = $string . "email= '" . $email . "'";

}

if (!empty($phone)) {

    if ($string != "") {
        $string = $string . "AND  ";
    }
    $string = $string . "phone_no= '" . $phone . "'";

}

if (!empty($street)) {

    if ($string != "") {
        $string = $string . "AND  ";
    }
    $string = $string . "Street_name= '" . $street . "'";

}

if (!empty($city)) {

    if ($string != "") {
        $string = $string . "AND  ";
    }
    $string = $string . "city= '" . $city . "'";

}

if (!empty($country)) {

    if ($string != "") {
        $string = $string . "AND  ";
    }
    $string = $string . "country= '" . $country . "'";

}

if ($string != "") {
    $string = "WHERE " . $string;
}

$connection = mysqli_connect('localhost', 'root', '', 'car_rental_system');

$query = mysqli_query($connection, "SELECT * FROM customer $string ");
$num_rows = mysqli_num_rows($query);

$i = 0;

if ($num_rows != 0) {
    while ($row = mysqli_fetch_assoc($query)) {
        $response[$i]['id'] = $row['customer_id'];
        $response[$i]['fn'] = $row['first_name'];
        $response[$i]['ln'] = $row['last_name'];
        $response[$i]['e'] = $row['email'];
        $response[$i]['phn'] = $row['phone_no'];
        $response[$i]['st'] = $row['Street_name'];
        $response[$i]['ct'] = $row['city'];
        $response[$i]['ctr'] = $row['country'];
        $data[$i] = $response[$i];
        $i += 1;
    }
}

mysqli_close($connection);
echo json_encode($data);