显示函数中的 php 数组元素

你好，我有以下数组，它是一个结果，形成一个基于（isset）调用的函数函数： list_activity_details_array（） 返回：

{"activity_related_to_id":"2","activity_id":"14","activity_type_icon":"fa fa-phone","activity_title":"call","activity_created_by":"User Last","activity_create_date":"03-08-2015","activity_due_date":"04-01-2015","acitvity_url_param":"contact_id","activity_details":"email and call details"})

如何查看 html 中的数组元素。 例如，如果字段activity_details。如何仅通过调用函数和元素来查看activity_details？

下面是显示数组的代码：

function list_activity_details_array(){
            global $connection;
        //$contact_id = $_REQUEST['contact_id'];
        $activity_id = $_REQUEST['activity_id'];
        $get = "SELECT * FROM activity_base WHERE activity_id = '$activity_id' "
                                    or die("Error: ".mysqli_error($connection));
        $query = mysqli_query($connection, $get);
    //Get activity base information
    $activity_array = array(); 
        while ($activity = mysqli_fetch_array($query)){
            $activity_related_to_id = $activity ['activity_related_to_id'];
            $activity_id = $activity['activity_id'];
            $activity_type_id = $activity['activity_type_id'];
      $activity_entity_type_id = $activity['activity_entity_type_id'];
            $activity_title = $activity['activity_title'];
            $activity_created_by = $activity['activity_created_by'];
            $activity_status_code_id = $activity['activity_status_code_id'];
            //$activity_type_icon;
      //Reverse Date  
      $activity_create_date = date("m-d-Y", strtotime($activity['activity_created_on']));
      $activity_due_date = date("m-d-Y", strtotime($activity['activity_due_date']));
            if ($activity_type_id == "1"){
                $activity_type_icon = "fa fa-envelope";
            }else if ($activity_type_id == "3"){
                $activity_type_icon = "fa fa-suitcase";
            }else if ($activity_type_id == "2"){
                $activity_type_icon = "fa fa-phone";
            }
      if ($activity_entity_type_id == "1") {
        $acitvity_url_param = "acct_id";
        $acitivty_is_for ="accounts_base";
        //$page_url = "account-profile.php";
      }else if ($activity_entity_type_id == "2") {
        $acitvity_url_param = "contact_id";
        $acitivty_is_for ="contacts";
        //$page_url = "contact-profile.php";
      }else if ($activity_entity_type_id == "3") {
        $acitvity_url_param = "contact_id";
        $acitivty_is_for ="contacts";
        //$page_url = "contact-profile.php";
      }
          //Get detailed activity information 
      //If activity is Email
    if ($activity_type_id == "1") {
        $email_details = email_activity_details($activity_id);
        while ( $email = mysqli_fetch_assoc($email_details)) {
          $activity_details = nl2br($email['email_message']);
        }
    }else if ($activity_type_id == "2") {
        $call_details = call_activity_details($activity_id);
        while ( $call = mysqli_fetch_assoc($call_details)) {
          $activity_details = $call['call_details'];
          }
        }else if ($activity_type_id == "3") {
        $meeting_details = meeting_activity_details($activity_id);
        while ( $meeting = mysqli_fetch_assoc($meeting_details)) {
          $activity_details = $meeting['meeting_details'];
          }
        }
        //Get creator user info
          $user_query = get_user_info($activity_created_by);
          while ($user = mysqli_fetch_array($user_query)) {
            $activity_created_by = $user['user_full_name'];
          }
          $activity_array['activity_related_to_id'] = $activity['activity_related_to_id'];
          $activity_array['activity_id'] = $activity['activity_id'];
          $activity_array['activity_related_to_id'] = $activity['activity_related_to_id'];
          $activity_array['activity_type_icon'] = $activity_type_icon; 
          $activity_array['activity_title'] = $activity['activity_title']; 
          $activity_array['activity_created_by'] = $activity_created_by; 
          $activity_array['activity_create_date'] = $activity_create_date; 
          $activity_array['activity_due_date'] = $activity_due_date; 
          $activity_array['acitvity_url_param'] = $acitvity_url_param; 
          $activity_array['activity_details'] = $activity_details; 
          $activity_array['activity_title'] = $activity['activity_title']; 
          $encode =  json_encode($activity_array);
          print_r($encode);
        }
    }
if (isset($_REQUEST['activity_id'])) {
    list_activity_details_array();
}