Hi Philip thanks, OK so when ANDing, is all that is being done is setting the result of anding to whichever bit is common to both, and with or ing, it's listing ALL bits present in both? Is that it?
If I understand correctly, if when PHP is defining an integer, which in this example in the book it is, if I perform bitwise operations on those integers, does PHP automatically see those integers as binary and treat them as such in bitwise operations? Dan -----Original Message----- From: Philip Hallstrom [mailto:[EMAIL PROTECTED] Sent: Monday, March 03, 2003 4:10 PM To: Dan Sabo Cc: [EMAIL PROTECTED] Subject: [PHP] RE: RE: Bitwise operator question Yes... it is the | operator that is doing it. >From the man pages: $a & $b And Bits that are set in both $a and $b are set. $a | $b Or Bits that are set in either $a or $b are set. So, let's say: $a = 5; # 0101 $b = 3; # 0011 Then: $a & $b 0101 & 0011 = 0001 (1) and $a | $b 0101 & 0011 = 0111 (7) does that help? It's not *summing* the values... although in your case it looks like it is... it's OR'ing them. On Mon, 3 Mar 2003, Dan Sabo wrote: > Thanks Philip, > > OK I understand the binary thing but that line, I just don't see it, It's > not the or operator that's summing up the two binary values is it? > > Dan > > -----Original Message----- > From: Philip Hallstrom [mailto:[EMAIL PROTECTED] > Sent: Monday, March 03, 2003 3:53 PM > To: Dan Sabo > Cc: [EMAIL PROTECTED] > Subject: RE: Bitwise operator question > > > Yes. Oops. > > -philip > > On Mon, 3 Mar 2003, Dan Sabo wrote: > > > Hi Phillip, > > > > Don't U mean > > > > 0001 > > | 0100 > > = 0101 > > > > ? > > > > Dan > > > > -----Original Message----- > > From: Philip Hallstrom [mailto:[EMAIL PROTECTED] > > Sent: Monday, March 03, 2003 2:33 PM > > To: Dan Sabo > > Cc: [EMAIL PROTECTED] > > Subject: Re: Bitwise operator question > > > > > > Here's how I think about it... > > > > CREATE_RECORDS = 1 in decimal and 0001 in binary. > > ALTER_RECORDS = 4 in decimal and 0101 in binary. > > > > that line returns a binary string where *any* of the bits are 1, so line > > them up: > > > > 0001 > > | 0101 > > = 0101 > > > > which is 5. > > > > On Mon, 3 Mar 2003, Dan Sabo wrote: > > > > > Hi, > > > > > > I'm reading the description of Bitwise Operators on page 81 of > > "Professional > > > PHP 4", the Wrox book. In the highlighted example on that page, the > line > > of > > > code... > > > > > > $user_permissions = CREATE_RECORDS | ALTER_RECORDS; > > > > > > the description in the book says that this line is building a set of > user > > > permissions out of the previously created constants with the OR operator > > (I > > > understand what OR means). The value of $user_permissions is set to > > either > > > 1 or 4, which is in fact 5 (0101). But how is this single line doing > > that? > > > The explanation was cryptic (to me). > > > > > > > > > > > > -- > > > PHP General Mailing List (http://www.php.net/) > > > To unsubscribe, visit: http://www.php.net/unsub.php > > > > > > > > > -- > > PHP General Mailing List (http://www.php.net/) > > To unsubscribe, visit: http://www.php.net/unsub.php > > > > -- > PHP General Mailing List (http://www.php.net/) > To unsubscribe, visit: http://www.php.net/unsub.php > > > > -- > PHP General Mailing List (http://www.php.net/) > To unsubscribe, visit: http://www.php.net/unsub.php > -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
