Finding if a number is a power of 2

Question

Just out of curiosity, how can you tell if a number x is a power of two (x = 2^n) without using recursion.

Thanks

Answer 1

If it's a power of 2? Well, one way is to convert it to binary, and verify the presence of only 1 1...:

$bin = decbin($number);
if (preg_match('/^0*10*$/', $bin)) {
    //Even Power Of 2
}