อัพเดตแก้ไขข้อมูลไม่ได้ เนื่องจาก $_GET

<?php
  session_start();
  include("connect/conn.php");
  include("header.php");
 
  if(isset($_POST['submit'])){
	if (isset($_SESSION['frmAction']) == isset($_POST['frmAction'])) {

        if(isset($_GET["emp_id"]))
        {
            $old_emp_id = $_GET["emp_id"]; 
        }
        
	$meSQL = "UPDATE  `employees`  SET ";
        $meSQL .= "emp_id = '$emp_id',";
        $meSQL .= "emp_username = '$emp_username',";
        $meSQL .= "emp_password = '$emp_password',";
        $meSQL .= "emp_name = '$emp_name',";
        $meSQL .= "emp_email = '$emp_email',";
        $meSQL .= "emp_phone = '$emp_phone'";
        $meSQL .= "emp_address = '$emp_address',";
        $meSQL .= "position = '$position',";
        $meSQL .= "set_rights = '$set_rights',";
        $meSQL .= "emp_pic = '$emp_pic'";
        $meSQL .= "WHERE emp_id='$old_emp_id'";

        $meQuery = mysqli_query($con,$meSQL);
        

		if ($meQuery == TRUE) {
            echo "<script language='javascript'> alert('บันทึกข้อมูลเรียบร้อย');window.location='employee-edit.php?emp_id=".$emp_id."';</script>";
		    } else {
                echo "<script language='javascript'> alert('มีปัญหาในการบันทึกข้อมูล กรุณาลองใหม่');window.location='employee-edit.php?emp_id=".$emp_id."';</script>";
		    }
		     
		}
}
  

  $id =  $_GET["emp_id"];
  $meSQL = "SELECT * FROM `employees` WHERE emp_id='$id' ";
  $meQuery = mysqli_query($con,$meSQL);
  $meResult = mysqli_fetch_assoc($meQuery);
  
  $emp_id = $meResult['emp_id'];
  $emp_username = $meResult['emp_username'];
  $emp_password = $meResult['emp_password'];
  $emp_name = $meResult['emp_name'];
  $emp_email = $meResult['emp_email'];
  $emp_phone = $meResult['emp_phone'];
  $emp_address = $meResult['emp_address'];
  $position = $meResult['position'];
  $set_rights = $meResult['set_rights'];
  $old_pic = $meResult['emp_pic'];