This "intelligence" is given by the laziness of the && operator.
$res = a() && b(); # if a() is false then b() does not evaluate
$res = a() & b(); # b() evaluates no matter a()'s result
so, order matters.
On Mon, Aug 10, 2009 at 3:29 PM, Andrew Ballard <aballard@xxxxxxxxx> wrote:
> On Mon, Aug 10, 2009 at 1:50 PM, Ralph Deffke<ralph_deffke@xxxxxxxx>
> wrote:
> > this is not "intelligence" its just pure math. the '&&' says if BOTH
> > expressions are true then the whole expression is true.
> >
> > so if the first one is false, the whole is false, why checking the next
> one
> > in the underlaying C it would be something like this
> > {
> > if ( expression == false ) return false;
> > if ( expression == false) return false;
> > return true;
> > }
> >
> > ralph
> > ralph_deffke@xxxxxxxx
>
> That's logically correct, and while PHP does implement this
> "short-circuit" logic, not all languages do. In that regard, I
> appreciate what John meant by saying it makes it look "more
> intelligent." Some languages evaluate each of the conditions to their
> respective boolean results before evaluating the logical operators.
>
> Andrew
>
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--
Martin Scotta
