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

The top answer:

($x & ($x - 1)) == 0

seemed to have issues with larger numbers for me, this works well for larger numbers using the same logic but with GMP:

gmp_strval(gmp_and($x, gmp_sub($x, 1))) == 0