-----Original Message-----
From: Ford, Mike [mailto:m.f...@leedsmet.ac.uk] 
Sent: 12 March 2013 10:51 AM
To: PHP General
Subject: RE: [PHP] Re: UNLESS Statement Equivalent

> unless ( $a and $b )
> =
> if ( ! ($a and $b) )
> So in simple terms, just stick a ! (or the keyword not) in front of 
> your expression, and you'll have exactly what you want:
> if( not ( ($current_page == $saved_page) and ($current_ip ==
> $saved_ip)
> and ($current_dt < ($saved_dt + 3600) ) ) {

Whilst this is true as far as it goes, I would suggest applying deMorgan's
laws to simplify slightly to

   if ( ($current_page != $saved_page) or ($current_ip != $saved_ip) or
($current_dt >= ($saved_dt + 3600) ) )

Also, the keyword versions of the Boolean operators are very low priority,
which is why you need all those extra parentheses -- if you switch to the
symbolic versions, you can leave all the internal parentheses out to give:

   if ($current_page != $saved_page || $current_ip != $saved_ip ||
$current_dt >= $saved_dt + 3600)


Mike, I presume you're saying the precedence of the Boolean keyword
operators is lower than the Boolean symbol operators, but if so then
wouldn't there be less need for the parentheses? I prefer using the Boolean
keyword operators for both the readability and because of the lower
precedence. Unless I've been wrong all this while and the keyword precedence
is actually higher?


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