将php变量保存为sql的null

Question

I have made a program to read 3 inputs on another page, the ID, code1, and code2.

One is a code to have easy to search, while the other 2 are variables that will be used to sum, subtract, multiply an divide and then save it all in a database

I have connected it to this php code:

if (isset($_POST["ID"]))
 {
    $id=($_POST["ID"]);
   $val1=($_POST["code1"]);
   $val2=($_POST["code2"]);

if ($val2 == 0){
    $sum = $val1 + $val2;
    $res = $val1 - $val2;
    $mul = $val1 * $val2;
    $div = NULL;
}else{
    $sum = $val1 + $val2;
    $res = $val1 - $val2;
    $mul = $val1 * $val2;
    $div = $val1 / $val2;
}

 $cnn=mysqli_connect("localhost","root","CC2CRO","ejercicios");
 if ($cnn) {
echo ("<SCRIPT LANGUAGE='JavaScript'>window.alert('CONEXION EXITOSA  
 !!!!')</SCRIPT>");         
    $sqlnr = mysqli_query($cnn, "INSERT INTO calculadora (Id, Valor1, 
 Valor2, Suma, Resta, Multiplicacion, Division) VALUES ('$id', '$val1', 
 '$val2', '$sum', '$res', '$mul', '$div')");

That is connected to MySQL database, so far it has worked, like for example I put OP45, 12, 3 when I see my database is saved as OP45 12 3 15 9 36 4 my issue is with when I use 0 for $val2, I wanted to save it as null since you can´t divide by 0, but when I run it it leaves the whole row empty, only does that when $val2 is 0, if $val2 is 1 or more it fills the entire row.

On my database Id is varchar and the rest are decimal (6,2), Id is PK and Not Null, also Valor1 and Valor2 are Not Null too.

below the code block from above I have this other one

 if ($sqlnr)
        echo ("<SCRIPT LANGUAGE='JavaScript'>window.alert('REGISTRO ALMACENADO CORRECTAMENTE !!!!')</SCRIPT>");
    else{
        echo ("<SCRIPT LANGUAGE='JavaScript'>window.alert('EL REGISTRO NO PUDO SER GUARDADO !!!!')</SCRIPT>");
    }

The first one is seen if it was saved in the database and the second one if it wasn't saved, so when val2 is 0 it always gives me the 2nd message.

Answer 1

You should change

$div = NULL;  to  $div = 'NULL';

then remove single quotes in '$div' in sql string ( '$div' to $div )

$sqlnr = mysqli_query($cnn, "INSERT INTO calculadora (Id, Valor1, 
        Valor2, Suma, Resta, Multiplicacion, Division) VALUES ('$id', '$val1', 
       '$val2', '$sum', '$res', '$mul', $div)");