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List:       php-db
Subject:    Re: [PHP-DB] undefined var has a value
From:       Rasmus Lerdorf <rasmus () php ! net>
Date:       2000-06-30 1:54:02
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> What's the value of the an undefined var in PHP?
> 
> if $undefined has never been defined before and I do this
> 
> ----------------------------
> if ($undefined == 0) echo "It has zero value";
> else echo "It has nozero value";
> ---------------------------
> 
> It seems to return zero value.
> This is not documented in the online PHP manual.
> Should I be expecting this in future releases or is this just fluke?

It's not a fluke.  It's like doing:

if('a'==0) echo "a is zero";

That doesn't mean that a is the same as zero, of course, but the numerical
equivalent of 'a' is 0 because PHP needs to convert one of the args in
order to do a sane comparison.  (int)'a' ends up evaluating to 0.  Same
goes for an undefined value.

There is a new operator in PHP 4 which does a strict equality on the two
arguments.

eg.   if('a'===0) "a is zero";

You will note that this does not print "a is zero" like the == version
does.

-Rasmus


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