如何通过PHP代码将Null值放在SQL服务器中

I have the following code, which will get values from these 9 variables and insert them in to a table. However, I don't know how to insert NULL value in to my table. As shown in line 10, if I try to use the keyword NULL, it consider as a string.

        $WorkOrder = $_POST['WorkOrder'];
        $Originated = $_POST['Originated'];
        $CustID = $_POST['CustID'];
        $Customer = $_POST['Customer'];
        $Contact = $_POST['Contact'];
        $Completed = $_POST['Completed'];
        $AccountNum = $_POST['AccountNum'];
        $Description = $_POST['Description'];
        $Status = $_POST['Status'];
        $Status = "NULL"; //Testing with NULL

        $insertquery = "INSERT INTO ElectronicShop(WorkOrder, Originated, CustID, Customer, Contact, Completed, AccountNum, Description, Status) 
                       VALUES ('$WorkOrder','$Originated','$CustID','$Customer','$Contact','$Completed','$AccountNum','$Description','$Status')";
        $data = sqlsrv_query($connectString, $insertquery) or die(print_r(sqlsrv_errors(SQLSRV_ERR_ALL), true));

I will be getting values for these 9 variables via text boxes in a webpage. So, I can't manually enter NULL in my query.

Instead of:

$insertquery = "INSERT INTO ElectronicShop(WorkOrder, Originated, CustID, Customer,  Contact, Completed, AccountNum, Description, Status) VALUES ('$WorkOrder','$Originated','$CustID','$Customer','$Contact','$Completed','$AccountNum','$Description','$Status')";

Use:

$insertquery = "INSERT INTO ElectronicShop(WorkOrder, Originated, CustID, Customer, Contact, Completed, AccountNum, Description, Status) VALUES
('$WorkOrder','$Originated','$CustID','$Customer','$Contact','$Completed','$AccountNum','$Description', NULL)";

You don't need to specify a variable for it, just write "NULL" without string marking signs (') into your query.

Greetz

Don't use the qoutes "":

$Status = "NULL";

Use:

$Status = null;

If you have not default value for Status column another than NULL, simply do not use this column in the columns list of insert statement.