PHP Gray Code - XOR error

Question

I wrote this function in php to do the Gray Code of a number:

function c_gray($num){
    $bin=decbin($num);  //binary of the number
    $xor=array();
    $xor[]=reset(str_split($bin)); //Get the first bit of binary and put it as the first element of $xor array
    for($i=0;$i<strlen($bin)-1;$i++){  //for any bit of the binary 
            echo $xor[]=$bin[$i] ^ $bin[$i+1]; //do the xor with the next bit of binary and put the result in array $xor
    }
    $res=implode($xor);  //put hte final code in $res
    return $res;
}

The problem is with the xor. if I print $xor array there is just the first element that i put with $xor[]=reset(str_split($bin));

Where I mistake?

Answer 1

Your string elements are not implicitly converted to ints ... try:

function c_gray($num){
    $bin   = decbin($num);  //binary of the number
    $xor   = array();
    $xor[] = reset(str_split($bin)); //Get the first bit of binary and put it as the first element of $xor array
    for($i=0;$i < strlen($bin)-1; $i++){  //for any bit of the binary
        $xor[] = (int)$bin[$i] ^ (int)$bin[$i+1]; //do the xor with the next bit of binary and put the result in array $xor
    }
    $res  = implode($xor);  //put hte final code in $res
    return $res;
}