json_encode 的局限 , 使用自定义的函数 .returnJson.

 $arr = array("liming", "tom", "green");

 $arr2 = array(
         1 => "liming",
         2 => "tom",
         3 => "lucy",
         4 => "jim"
     );

     echo json_encode($arr2)."\n";

            function returnJson($arr)
         {
             $str = "[";
             $num = 0;
             foreach ($arr as $k => $v)
             {

                 if($num == count($arr) - 1)
                 {
                     $str.="'".$v."'";
                 }
                 else
                 {
                     $str.="'".$v."',";
                 }

                 $num++;
             }
             $str .="]";
             return $str;
         }

         echo returnJson($arr2);

结果: