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用PHP和MySQL构建一个数据库驱动的网站(7)

WBOY
Release: 2016-06-21 09:10:50
Original
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mysql|数据|数据库

现在我们已经有了允许用户输入一个笑话并将其加入到我们的数据库中的程序代码。现在剩下的就是将其加入到我们已做好的笑话显示页面。因为绝大多数的用户只会想要看看笑话,所以我们不想对我们的页面做大的更改,除非用户表示想要添加一个新的笑话。因为这个原因,我们的应用程序应该是一个多功能的页面。下面是程序的代码:



...


  // If the user wants to add a joke
  if (isset($addjoke)):
?>

Type your joke here:






  else:

    // Connect to the database server
    $dbcnx = @mysql_connect("localhost",
             "root", "mypasswd");
    if (!$dbcnx) {
      echo( "

Unable to connect to the " .
            "database server at this time.

" );
      exit();
    }

    // Select the jokes database
    if (! @mysql_select_db("jokes") ) {
      echo( "

Unable to locate the joke " .
            "database at this time.

" );
      exit();
    }

    // If a joke has been submitted,
    // add it to the database.
    if ("SUBMIT" == $submitjoke) {
      $sql = "INSERT INTO Jokes SET " .
             "JokeText='$joketext', " .
             "JokeDate=CURDATE()";
      if (mysql_query($sql)) {
        echo("

Your joke has been added.

");
      } else {
        echo("

Error adding submitted joke: " .
             mysql_error() . "

");
      }
    }
      echo("

Here are all the jokes " .
         "in our database:

");
      // Request the text of all the jokes
    $result = mysql_query(
              "SELECT JokeText FROM Jokes");
    if (!$result) {
      echo("

Error performing query: " .
           mysql_error() . "

");
      exit();
    }
      // Display the text of each joke in a paragraph
    while ( $row = mysql_fetch_array($result) ) {
      echo("

" . $row["JokeText"] . "

");
    }
    // When clicked, this link will load this page
    // with the joke submission form displayed.
    echo("

" .
         "Add a Joke!

");
    endif;
  ?>





  现在我们有了一个单独的文件,这个文件包含不太多的PHP代码,通过这个文件,我们可以显示我们的MySQL数据库中的笑话并能向我们的MySQL数据库中添加笑话。

一个挑战

  作为家庭作业,你可以看看你是不是能解决这么一个问题:在页面上显示的每一个笑话后面放置一个叫“Delete this Joke”的超连接,当单击这个连接时,会从数据库中删除这个笑话并显示更改过以后的笑话列表。下面是对你的一些提示:

  你可以还在一个多功能页面完成全部的功能。

  你需要使用SQL的DELETE命令,这个命令我们曾在第二章中学习过。

  这是一个关键的问题。要删除一个指定的数据库,你需要能够唯一地标识它。Jokes表中的ID可以完成这个功能。你必须将要被删除的笑话的ID传递到删除笑话的请求中。将这个值放到“Delete this Joke”连接的查询字符串中是比较合适的。

  如果你觉得你已经有了答案,或者你只想知道解决方案,那就去看看下一页。祝你好运!

结语

  在这一章中,我们学习了一些新的用来实现与MySQL数据库服务接口的PHP函数。使用这些函数,我们建立了我们的第一个数据库驱动的网站,我们的这个网站可以在线地发布我们数据库中笑话并允许访问者向其中添加他们自己的笑话。

  在第五章中,我们会回到MySQL命令行去学习如何使用关系型数据库的原理以及其他一些更高级的SQL查询去描述更为复杂的信息,并给予访问者对他们自己添加的笑话以特别的权限!

挑战的解决

  这是我们上面提出的“家庭作业”的解决方案。要在每一个笑话后面添加一个“Delete this Joke”连接,必须作下面的改动:

  之前,我们曾经在我们的页面的底端的“Add a Joke!”连接中传递过一个$addjoke变量,通过这个变量来通知我们的脚本不再显示通常的笑话列表,而是显示一个录入笑话的表单。与此相类似,我们在我们的“Delete this Joke”连接中传递一个$deletejoke变量来表示我们想要删除一个笑话。

  在获得每一个笑话的JokeText列的同时,我们还获得了ID列的值,所以我们获得了与数据库中每一个笑话关联的ID。

  我们将要删除的笑话的ID值赋予$deletejoke变量。这是通过将从数据库中获得的ID值插入到每一个笑话的“Delete this Joke”连接中来实现的。

  使用了一个if 语句,如果在载入这一页时,我们的$deletejoke被赋予了一个值(使用isset函数),我们会在一个SQLDELETE语句中使用这个值(将被删除的笑话的ID)来删除指定的笑话。

  这儿是全部的源代码:



...

  // If the user wants to add a joke
  if (isset($addjoke)):
?>


Type your joke here:





  else:

    // Connect to the database server
    $dbcnx = @mysql_connect(
               "localhost", "root", "mypasswd");
    if (!$dbcnx) {
      echo( "

Unable to connect to the " .
            "database server at this time.

" );
      exit();
    }

    // Select the jokes database
    if (! @mysql_select_db("jokes") ) {
      echo( "

Unable to locate the joke " .
            "database at this time.

" );
      exit();
    }
    // If a joke has been submitted,
    // add it to the database.
    if ("SUBMIT" == $submitjoke) {
      $sql = "INSERT INTO Jokes SET " .
             "JokeText='$joketext', " .
             "JokeDate=CURDATE()";
      if (mysql_query($sql)) {
        echo("

Your joke has been added.

");
      } else {
        echo("

Error adding submitted joke: " .
             mysql_error() . "

");
      }
    }

    // If a joke has been deleted,
    // remove it from the database.
    if (isset($deletejoke)) {
      $sql = "DELETE FROM Jokes " .
             "WHERE ID=$deletejoke";
      if (mysql_query($sql)) {
        echo("

The joke has been deleted.

");
      } else {
        echo("

Error deleting joke: " .
             mysql_error() . "

");
      }
    }
      echo("

Here are all the jokes " .
         "in our database:

");
      // Request the ID and text of all the jokes
    $result = mysql_query(
                "SELECT ID, JokeText FROM Jokes");
    if (!$result) {
      echo("

Error performing query: " .
           mysql_error() . "

");
      exit();
    }
    // Display the text of each joke in a paragraph
    // with a "Delete this Joke" link next to each.
   while ( $row = mysql_fetch_array($result) ) {
      $jokeid = $row["ID"];
      $joketext = $row["JokeText"];
      echo("

$joketext " .
           "" .
           "Delete this Joke

");
    }
    // When clicked, this link will load this page
    // with the joke submission form displayed.
    echo("

" .
         "Add a Joke!

");
    endif;
  ?>






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