leetcode 幸运数字 202. Happy Number

Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

Example: 

Input: 19
Output: true
Explanation: 
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

    function isHappy($n) {
    
     $num=0;
     while ($n!=1){
         $arr=str_split($n);
         $bb=0;//求平方和

         foreach ($arr as $k=>$v){
             $bb=$bb+$v*$v;
         }
         $n=$bb;
         $num=$num+1;
        // echo $n."\n";
         if($num>100){
             return false;
         };
     }
     return true;
    }