$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);