Zero and NULL

[jakeone]

Hello,

I have a form with a text field (<input name="a1" type="text" size="5">). If a user types "0", "0.0" or "0.00" , I want to insert "0" into my mysql db. If a user leaves the field blank, I want to insert NULL into the db.

However, my code keeps inserting "0" into my db even when the field is left blank. (I echoed out the variable and it's empty - so I don't know why PHP doesn't treat it as NULL).

To check what was happening, I wrote:

if (is_null($a1))
{
echo "a1 is NULL";
}
else echo "a1 is NOT NULL";

As I say, when I echoed out $a1 to double-check, it's empty but the above code keeps saying "a1 is NOT NULL". What am I doing wrong? Any pointers would be appreciated.

[onyx]

Is your database set up to allow null values for that field?

[jakeone]

Hi Onyx,

Yes, it does allow NULL values.

Cheers.

Jake

[mazsolt]

The problem could be, that if a user leaves blank the text field a1, the field a1 is empty, it isn't null.
if you send the values using the "get" posting, you can see in the query string:

?...&a1=&

So it's better to check the length of the field:

if (!strlen($_GET["a1"]))

To be sure that the user introduce only numerical digits, use regular expressions (with ereg)

[onyx]

I usually check to see if the field is an empty string and if so I specifically set the value in the SQL to be null or in the case that it is null by default then I just do not include it in the sql at all.