[pmwiki-devel] php logic question

[Patrick R. Michaud]

On Wed, Mar 14, 2007 at 08:58:44AM +0100, christian.ridderstrom at gmail.com wrote:
> On Tue, 13 Mar 2007, Hans wrote:
> >>        if (!$page || !$permit)
> 
> Ok. I was wondering if $page was a string, in which case I'm not sure if 
> something like
> 
> 	!""
> 
> if true or false.

In PHP, the expression !"" evaluates to true.

When treated as a boolean, both the empty string and "0" evaluate to
false, while all other strings are treated as true.  Thus !"" is
equivalent to !(false), which results in true.

More information about the treatment of boolean values 
in PHP can be found at 
http://www.php.net/manual/en/language.types.boolean.php#language.types.boolean.casting

Pm