Re: algorythm question

ok, now it's clear why i must use '|' instead of '+'. i still couldn't get what happens with bits but you don't have to explain more. i know that it's about bitwise operators, and how they handle numbers. no! ok! i just got it! thank you again. --- bob parker <bob_parker@dodo.com.au> wrote: > Couple of points: > You really do need to use the '!' operator to > combine the categories not '+' > eg if your user entered 2 twice you would get > $userLevels = 2 + 2; // wrong we just made our admin > a writer > but > $userLevels = 2 | 2; // ok is still admin because > $userLevels is still 2 > > These operators, | and & are called bit wise > operators to see how they > work look at the binary representations of the > numbers > say $userlevel = 15 then in binary > $userlevel is 1111 > $result = 1111 & 0001; // $result is 0001 binary or > decimal 1 > $result = 1111 & 0010; // $result is 0010 binary or > decimal 2 > $result = 1111 & 0100; // $result is 0101 binary or > decimal 4 > $result = 1111 & 1000; // $result is 1000 binary or > decimal 8 > the '&' operator only returns the bit or bits which > are both 1 in the > same column. > > The or operator returns the bits which are 1 in > ether column so > 2 | 2 which is 0010 | 0010 still returns 0010 which > is 2 > Hope this helps > bob __________________________________________________ Do you Yahoo!? New DSL Internet Access from SBC & Yahoo! http://sbc.yahoo.com