Insert Two Checkbox data in one column Database

I have two checkbox

Ticket : 
        <input type="checkbox" name="ticket[]" value="read">Read
        <input type="checkbox" name="ticket[]" value="write">Write
        <input type="checkbox" name="ticket[]" value="edit">Edit
User : 
        <input type="checkbox" name="user[]" value="read">Read
        <input type="checkbox" name="user[]" value="write">Write
        <input type="checkbox" name="user[]" value="edit">Edit

insert code

$dbServerName = "localhost";
$dbUserName = "root";
$dbPassword = "";
$dbName = "test";

$conn = mysqli_connect($dbServerName, $dbUserName, $dbPassword, $dbName);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
$checkbox = implode(',', $_POST);
$sql = "INSERT INTO checkbox (checkbox)
VALUES ('$checkbox')";

if ($conn->query($sql) === TRUE) {
    echo "New record created successfully";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

Table

How to insert two checkbox data in one column. only one checkbox data insert in database.