php while循环得到循环次数

<?php
   $link = mysql_connect('localhost','root','pwd');
   mysql_select_db('db'); 
   $sql = "select region_id,local_name from regions where region_grade=1";
   $result = mysql_query($sql);
 $i =0;
  while ($row= mysql_fetch_assoc($result)) {
        $list[$i]['text']=$row['local_name']; 
        $list[$i]['value']=$row['region_id'];
        $i++;      
   }
  $list = json_encode($list);
  echo   $list;
?>