Re: [PHP] Re: Difference between & &&

[Leif K-Brooks]

Not sure where you can read more, but let me try to explain it.  The 
bitwise operators operate on a binary representation of a number.  4 is 
100 in binary, 5 is 101.  5 | 4 results in 5, because the | operator 
sets bits set in either number.  5 & 4 results in 4, because the & 
operator only sets bits set in both.  As for 4 & 4, the same bits are 
set in both 4 and 4 (since they're the same number! :)), so it results 
in the same number.

James Taylor wrote:

Where can I read more about this?  I'm not sure that I understand why 4
& 4 == 4.
-----Original Message-----
From: Greg Beaver [mailto:[EMAIL PROTECTED] 
Sent: Friday, March 07, 2003 11:04 PM
To: [EMAIL PROTECTED]; James Taylor
Subject: [PHP] Re: Difference between & &&

Hi James,

& is a bit-wise AND.  && is a logical AND.  The bitwise AND will return 
a number, the logical AND will return true or false boolean values. 
It's a subtle distinction, but important.  4 & 4 == 4  4 && 4 == true ==
1

Regards,
Greg
--
phpDocumentor
http://www.phpdoc.org
James Taylor wrote:
 

Ok, this may have already been posted to the list already, but the 
archives don't seem to like the & and && characters.

I'm running into some code that looks like this:

<snip>
Define('INPUT', 2);
<snip>
if($search->level & INPUT) $tmp.= $search->input();
Ok, what's the & mean?

As far as I could tell from the very little documentation I was able 
to scrape up on google, & is a bit-by-bit operator.  Thus, if either 
INPUT or $search->level, we get TRUE... If that's the case, what's the
   

 

point of using it instead of || ?

Or, do I just totally not understand the point of this.  Thanks

   



 

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