สอบถามเรื่องการระบุวันที่และเวลาที่แก้ไขข้อมูลในตัว PHP add/edit/delete mysql on same page หน่อยครับ

//*** Add Condition ***//
if($_POST["hdnCmd"] == "Add")
{
	$strSQL = "INSERT INTO customer ";
	$strSQL .="(CustomerID,Name,Email,CountryCode,Budget,Used,Last_edit) ";
	$strSQL .="VALUES ";
	$strSQL .="('".$_POST["txtAddCustomerID"]."','".$_POST["txtAddName"]."' ";
	$strSQL .=",'".$_POST["txtAddEmail"]."' ";
	$strSQL .=",'".$_POST["txtAddCountryCode"]."','".$_POST["txtAddBudget"]."' ";
        $strSQL .=",'".$_POST["txtAddUsed"]."' ";
	$strSQL .=", NOW() ) ";
	$objQuery = mysql_query($strSQL);
	if(!$objQuery)
	{
		echo "Error Save [".mysql_error()."]";
	}
	//header("location:$_SERVER[PHP_SELF]");
	//exit();
}

//*** Update Condition ***//
if($_POST["hdnCmd"] == "Update")
{
	$strSQL = "UPDATE customer SET ";
	$strSQL .="CustomerID = '".$_POST["txtEditCustomerID"]."' ";
	$strSQL .=",Name = '".$_POST["txtEditName"]."' ";
	$strSQL .=",Email = '".$_POST["txtEditEmail"]."' ";
	$strSQL .=",CountryCode = '".$_POST["txtEditCountryCode"]."' ";
	$strSQL .=",Budget = '".$_POST["txtEditBudget"]."' ";
	$strSQL .=",Used = '".$_POST["txtEditUsed"]."' ";
        $strSQL .=",Last_edit = NOW() ";
	$strSQL .="WHERE CustomerID = '".$_POST["hdnEditCustomerID"]."' ";
	$objQuery = mysql_query($strSQL);
	if(!$objQuery)
	{
		echo "Error Update [".mysql_error()."]";
	}
	//header("location:$_SERVER[PHP_SELF]");
	//exit();
}