选择标记不将数据传递给php

Question

我正在注册表格，我在其中有些字段可以正常工作，但是当我添加性别部分时，我的PHP无法识别$ _POST变量中的性别。 以下是我的HTML：

<div class="form-group label-floating is-select">
                                        <label class="control-label">Your Gender</label>
                                        <select class="selectpicker name="gender" form-control" size="auto">
                                            <option value="MA">Male</option>
                                            <option value="FE">Female</option>
                                        </select>
                                    </div>

以下是我的php：

if (isset($_POST['regButton'])) {

        $i = 0;

        $username = strtolower($_POST['fname'] . $_POST['lname'] . $i++ );
        $password = $_POST['password'];
        $FirstName = $_POST['fname'];
        $LastName = $_POST['lname'];
        $usermail = $_POST['email'];
        $dob = $_POST['datetimepicker'];
        $gender = $_POST['gender'];

        $query = "INSERT INTO users(username, password, FirstName, LastName, Email, dob, gender) ";
        $query .= "VALUES ('$username', '$password', '$FirstName', '$LastName', '$usermail', '$dob', '$gender')";

        $result = mysqli_query($con, $query);

        if(!$result){

            echo "<div class='alert alert-danger'>Query Failed.</div>";
        }else {

            echo "<div class='alert alert-danger'>Registraation Successful.</div>";
        }

    }

我该怎么办？请帮帮我。