How to reverse bits of a byte?

Question

For example, in PHP, how would I reverse the bits of the byte 11011111 to 11111011?

Answer 1

This is O(n) with the bit length. Just think of the input as a stack and write to the output stack.

My attempt at writing this in PHP.

function bitrev ($inBits, $bitlen){
   $cloneBits=$inBits;
   $inBits=0;
   $count=0;

   while ($count < $bitlen){
      $count=$count+1;
      $inBits=$inBits<<1;
      $inBits=$inBits|($cloneBits & 0x1);
      $cloneBits=$cloneBits>>1;
   }

    return $inBits;
}