Need to change to NULL if variable = 0

[zelig]

Okay, so, I have a script that allows a forum inside of a room in a game.

 

If you want a forum, you mark Yes from a dropdown menu inside the editing portion of the room. It will then save that room's title into a field called `board` in the database.

 

However, when you mark No from the dropdown, it still leaves it in there. I don't want this. I want it to change to NULL.

 

How do I go about doing this?

 

Here's my current coding:

 

if (!islevel($p,$co)) newlevel($p,$co);
setlevel($p,$co,"title",filter(stripslashes($title)));
setlevel($p,$co,"board",filter(stripslashes($title)));
}

 

Explanations:

setlevel just connects to the database and inserts these values.

$title is obviously the title of the room

$co = coordinates for the room

 

Here is the editing page, where the dropdown menu is:

 

 

<table width=100% style=text-align:center><tr>

<td>BOARD:<br />

<select name=b>

  <option value=0>No</option>

  <option value=1 <? if ($b == 1) echo "selected"

  ?>>Yes</option></select><br />Was <?=$b?>

</tr></table>

 

 

[AyKay47]

we can't help you with this without seeing all of the relevant code.

[zelig]

Good point. Here it is:

 

Input form:

 

<form action=levedit.php method=post>

<table border=0><tr>

<td>

TITLE:<br>

<input type=text name=title value="<?=$title?>">

<table width=100% style=text-align:center><tr>

<td>BOARD:<br />

<select name=b>

  <option value=0>No</option>

  <option value=1 <? if ($b == 1) echo "selected"

  ?>>Yes</option></select><br />Was <?=$b?>

</tr></table>

 

<input type=hidden name=p value=<?=$p?>><input type=hidden name=co value=<?=$c?>><input type=hidden name=username value=<?=$username?>><input type=hidden name=password value=<?=$password?>><input type=hidden name=no value=<?=$no?>>

<input type=submit value="Edit Level"> <input type=reset value=Reset>

 

Levedit.php:

<?
require("function.s");
if (!is_numeric(get("admin"))){
if (!islevel($p,$co)) newlevel($p,$co);
setlevel($p,$co,"title",filter(stripslashes($title)));
if(b == 1) setlevel($p,$co,"board",filter(stripslashes($title)));
if(b == 0) setlevel($p,$co,"board",NULL);
echo "Level editted/created.<br>\n";
}
?>

 

The setlevel and islevel functions (from function.s):

 

function islevel($world,$coords){
$data = false;
$dbh=dbconnect() or die ('IsUser error: ' . mysql_error()."<br>");
mysql_select_db("XX");
$result = mysql_query("SELECT * FROM levels WHERE coords = '$coords' AND world = '$world'");
if (mysql_num_rows($result) > 0) $data = true;
mysql_close($dbh);
return $data;
}

 

function setlevel($world,$coords,$var,$value){
$value = str_replace("'","'",$value);
$dbh=dbconnect() or die ('SetUser error: ' . mysql_error()."<br>");
mysql_select_db("XX");
if(is_numeric($value)) mysql_query("UPDATE levels SET $var = $value WHERE coords = '$coords' AND world = '$world'"); else mysql_query("UPDATE levels SET $var = '$value' WHERE coords = '$coords' AND world = '$world'");
mysql_close($dbh);
return 1;
}

[batwimp]

I've never sent NULL like that to a function, so I'm not sure it will propagate all the way into your database the way you want it to. You may try echoing out the completed mySQL query (assign it to a variable first) and see if it contains the correct information. I would recommend assigning to the field something besides NULL in this case, like the string "None" or something that would be easier to write to/check against down the road. But that's just me.

[zelig]

Okay, I've got it to put a 0 in now, but I thought there was a way for it to change that column in the `board` field to NULL...

 

Updated portion:

 

if($b == 1) setlevel($p,$co,"board",filter(stripslashes($title)));
if($b == 0) setlevel($p,$co,"board",$b);

[batwimp]

There is, but you would probably have to check for it inside the function, then add NULL to the DB query. Like I said, I've never done it before, so maybe one of the gurus here can help you with the specifics.

[zelig]

Ah, okay.

 

Thanks batwimp!

[AyKay47]

I would simply set the arg $value to null as default:

 

setlevel($world,$coords,$var,$value = null)

 

Then, if $b == 0, do not pass a value for that arg:

 

if($b == 0) setlevel($p,$co,"board");

 

which will keep $value as NULL in your function.

 

Depending on your logic for this, the best option would be to change the mysql field definition to default NULL, changing the value when yes is selected.

[zelig]

Hmm, all that did was delete out all the info, but not checkmark the field as being NULL.

 

Question: What exactly is the difference between a blank field and one that is checkmarked as NULL? Is there even anything that I need to worry about, or is it pretty much the same thing?

[batwimp]

But it also needs to be put back to NULL once a value is already in there if the user selects it. A default value in MySQL won't do that if he's doing an update. Will it?

[AyKay47]

Question: What exactly is the difference between a blank field and one that is checkmarked as NULL? Is there even anything that I need to worry about, or is it pretty much the same thing?

 

check marked as null?

 

But it also needs to be put back to NULL once a value is already in there if the user selects it. A default value in MySQL won't do that if he's doing an update. Will it?

 

I'm trying to wrap my head around the logic here, but I haven't been given enough information, so it's hard to tell.

[zelig]

Marked as null. In the MySQL DB, there's a checkmark to indicate that it is null.

[AyKay47]

Marked as null. In the MySQL DB, there's a checkmark to indicate that it is null.

 

Oh, right, how are these values initially being inserted?

[zelig]

Through the input form near the top of the post.