มันขึ้นแบบนี้แก้ยังไงครับ Fatal error: Call to a member function query() on a non-object in C:\AppServ\www\shops\php\test.php on line 15

<?php 
    require_once('connect.php');

    $id = $_POST['id'];
    $detail = $_POST['detail'];
    $action = $_POST['action'];

    if($action == 'Insert') insert();

    function insert(){
     global $conn;  //เพิ่มส่วนนี้
        $id = $_POST['id'];
        $detail = $_POST['detail'];

        $sql ="insert into test (id, detail) value('$id','$detail')";
        if($conn->query($sql) === TRUE){
            echo"บันทึกข้อมูลแล้ว";
        }else
            echo"บันทึกข้อมูลไม่สำเร็จ";
    }
    
?>