01 to 1

function bin2dec($str) {
    $str_ary = str_split($str);
    $result = 0;
    foreach ($str_ary as $key => $value) {
        $result += $value * pow(2, (count($str_ary) - 1 - $key));
    }
    return $result;
}

echo(bin2dec(110101));