AZ算法

如果A=1 Z=26，输入1000，则是ALL 递归算法

function math($num){
$res = array();
$res['tail'] = $num%26;
$res['head'] = floor($num/26);
if($res['head'] > 26) {
math($res['head']);
}else{
echo $res['head'];
}
echo $res['tail'];
}

$res = math(1000);