function explanation **quicky**

[scottybwoy]

Hi I have this function :

<?php

function isodd($int) {
return($int & 1);
}

?>

 

It does exactly what it says on the tin.

 

However How does it know that the $int isodd?  Can someone explain please, thanks.

[scottybwoy]

Basically I don't understand the & bit.

[aschk]

That is logical AND syntax.

e.g.

 

if $int = 4 then in binary it is 00000100

and 1 is 00000001

 

so doing the logical AND of these gives you:

 

00000100

00000001

=======

00000000

 

Which as you can see is 0, or false...

 

Can you see how it works for an odd number now?

[scottybwoy]

OK, I see.

 

So as it's a logical comparison all binary odd's having the 8th digit as 1 then it returns false whenever there is not a 1 for the 8th bit, correct?

[aschk]

Yes essentially.

So for 87 (01010111) the right most bit is a 1, so doing 1 & 1 (or TRUE AND TRUE) you get TRUE (1) thus working for odd numbers.