如何显示消息，如果没有结果返回数据库查询在PHP

Question

想知道是否有人可以帮助。我通过PHP和MySQL的教程运行，那里是持有一个笑话数据库：

• 笑话的笑话表
• 作者在作者表中类别表
• 分类

我有一个名为authors.html.php的页面，其中包含一个作者列表，其中包含添加作者，编辑/删除作者（每个返回作者姓名旁边）的选项。我所试图做的是如果包含作者的数据库是空的，而不是显示下面的PHP错误：

Notice: Undefined variable: authors in C:\wamp\www\chapter7\admin\authors\authors.html.php on line 22

我想显示一个漂亮整洁的消息说，没有找到结果。

我的代码如下：

<?php 
    include $_SERVER['DOCUMENT_ROOT'] . '/chapter7/includes/db.inc.php'; 
    try { 
      $result = $pdo->query('SELECT id, name FROM author'); 
    } catch (PDOException $e) { 
      $error = 'Error fetching authors from the database!'; 
      include $_SERVER['DOCUMENT_ROOT']. 
          '/chapter7/admin/error.html.php'; 
      exit(); 
    }  

    foreach ($result as $row){ 
      $authors[] = array('id' => $row['id'], 'name' => $row['name']); 
     } 

    include 'authors.html.php'; 

    if (isset($_POST['action']) and $_POST['action'] == 'Delete') { 
      include $_SERVER['DOCUMENT_ROOT']. 
          '/chapter7/includes/db.inc.php'; 
      //Get jokes belonging to author 
      try { 
       $sql = 'SELECT id FROM joke WHERE authorid = :id'; 
       $s = $pdo->prepare($sql); 
       $s->bindValue(':id', $_POST['id']); 
       $s->execute(); 
      } catch (PDOException $e) { 
       $error ='Error getting list of jokes to delete.'; 
       include $_SERVER['DOCUMENT_ROOT']. 
           '/chapter7/admin/error.html.php'; 
       exit(); 
      } 
      $result = $s->fetchAll(); 
      //Delete joke category entries 
      try { 
       $sql = 'DELETE FROM jokecategory WHERE jokeid =:id'; 
       $s = $pdo->prepare($sql); 
       //For each joke 
       foreach ($result as $row) { 
         $jokeId= $row['id']; 
         $s->bindValue(':id', $jokeId); 
         $s->execute();  
       } 
      } catch (PDOException $e) { 
       $error = 'Error deleting category entries for joke.'; 
       include $_SERVER['DOCUMENT_ROOT']. 
           '/chapter7/admin/error.html.php'; 
       exit(); 
      } 
      //Delete jokes belonging to author 
      try { 
       $sql = 'DELETE FROM joke WHERE authorid = :id'; 
       $s = $pdo->prepare($sql); 
       $s->bindValue(':id', $_POST['id']); 
       $s->execute(); 
      } catch (PDOException $e) { 
       $error = 'Error deleting jokes for author'; 
       include $_SERVER['DOCUMENT_ROOT']. 
           '/chapter7/admin/error.html.php'; 
       exit(); 
      } 
      //Delete the author 
      try { 
       $sql = 'DELETE FROM author WHERE id =:id'; 
       $s = $pdo->prepare($sql); 
       $s->bindValue(':id', $_POST['id']); 
       $s->execute(); 
      } catch (PDOException $e) { 
       $error ='Error deleting author'; 
       include $_SERVER['DOCUMENT_ROOT']. 
          '/chapter7/admin/error.html.php'; 
       exit(); 
      } 
      header('Location: .'); 
      exit(); 
    }  

请注意我非常新的这个和已经尝试了一些反复失败的悲惨，所以任何帮助，甚至只是简单的指导，将步骤我通过思考围绕创建这样的功能将不胜感激。不只是寻找正确的答案，而是想要了解如果任何人都可以提供帮助的背后的想法会很棒。

Answer 1

类似的东西应该工作。我过去曾经使用过它，它已经为我工作。你将需要调整查询等到你的数据库和表格，但它应该没问题。

$stm = $PdoObj->prepare("SELECT * FROM NEWS_articles"); 
    $stm ->execute(); 
    $results = $stm ->fetchAll(); 

    if($results==null){ 
     echo "<p>No dice, try other criteria</p>"; 
    }else{ 
     foreach($results as $row){ 
      echo $row["articleName"]; 
     } 
    }