----- Original Message -----
From: "JD" <jd_borozo@xxxxxxxxxx>
To: <php-general@xxxxxxxxxxxxx>
Sent: Friday, September 08, 2006 11:03 PM
Subject: if statement with or comparison (newbie)
I'm trying to set up a simple conditional, something like this:
If my_variable is NOT equal to (black or white)
echo "wrong color"
else
echo "right color"
Here is what I have tried:
if ($_REQUEST['id'] != ("black" or "white")) {
What PHP (and any parser, for that matter) will try to do is first solve the
innermost parenthesis. ("black" or "white"). Many typed languages would
give an error at this point, but PHP tries to convert anything it gets to
whatever is more useful at the moment. Since both "black" and "white" are
not null or empty strings, they are evaluated as true for the logical
comparison and true or true is always true. Now, $_REQUEST['id'] might be
whatever it is, but dealing with booleans as we are this far, anything but
missing or empty string will be true as well, which will give you the second
option.
Now, first of all, avoid negative comparissons, negative booleans are
horrible. Try first to straighten them up or you might get thoroughly
confussed:
if ($_REQUEST['id] == 'black' or $_REQUEST['id'] == 'white') {
echo 'right color';
} else {
echo 'wrong color'';
}
And so as you know why it is good to straighten negative booleans, this
would be the twisted way
if ($_REQUEST['id] != 'black' and $_REQUEST['id'] != 'white') {
echo 'wrong color'';
} else {
echo 'right color';
}
Notice that not only the comparisson changed but now they are joined by an
AND instead of an OR and the then and else parts are swapped.
Satyam
echo "wrong color";
} else (
echo "right color";
)
However, no matter what I enter, I always get response "right color".
I should add that if I change the if statement to:
if ($_REQUEST['id'] != ("black"))
then I get "right color" when I enter "black" and "wrong color" for
everything else.
Would you please point out what's the trivial thing I'm missing here...
jd
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