php - 通过 PHP 选择表单从数据库中删除条目 - 不删除条目

Question

我正在尝试使用 HTML 表单从数据库中删除条目。但是，提交后，该条目不会从数据库中删除，也不会显示任何错误代码来说明原因。

如果我在代码中遗漏了某些内容，如果我忽略了某些内容，有人可以让我知道吗？

谢谢。

<form method="post" action="./removeBook.inc.php">
<select name="books">
<option>Please select the Book you wish to delete:</option>
<?php
try {
    $dsn = "mysql:host=csdm-mysql;dbname=db1001550_book_management";
    $username = "1001550";
    $password = "1001550";
    // try connecting to the database
    $con = new PDO($dsn, $username, $password);
    // turn on PDO exception handling 
    $con->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
    // enter catch block in event of error in preceding try block
    echo "Connection failed: " . $e->getMessage();
}

try {                                          
    $sql=("SELECT * FROM books");                                          
    $results = $con->query($sql);                                                                                  
    if ($results->rowcount() == 0) {
        echo "<p>No books found. </p><br />";
    } else {     
        foreach ($results as $row) {
            $book_id=$row['book_id'];                                    
            echo "<option value=\"".$book_id."\">".$book_id."</option>";
        } 
    }
} catch (PDOException $e) {
    echo "Query failed: " . $e->getMessage();
}

mysql_close();
?>

</select>
<input type="submit" name="submit" value="Remove Book" style="width:auto;">
</form>

这是表单提交页面中的代码:

<?php                            
$host="csdm-mysql"; // Host name 
$username="1001550"; // Mysql username 
$password="1001550"; // Mysql password 
$db_name="db1001550_book_management"; // Database name  

// Connect to server and select database.
mysql_connect("$host", "$username", "$password")or die("cannot connect"); 
mysql_select_db("$db_name")or die("Cannot select DB");

if (isset($_POST['books'])) {
    $books=$_POST['books']; 
}

// Remove data from database 
$result=mysql_query("DELETE FROM books WHERE book_id=$books");

// if successfully deleted from database, prompt will say book was deleted. 
if ($result) {
    print "<script type=\"text/javascript\">";
    print "alert('Book has been deleted successfully!')";
    print "</script>";
} else {
    print "<script type=\"text/javascript\">";
    print "alert('Book was not deleted')";
    print "</script>";
}

// close connection
mysql_close();
?>

<form method="post" action="./removeBook.inc.php">
                              <select name="books">
                                  <option>Please select the Book you wish to delete:</option>
                                  <option value='B0001'>B0001</option><option value='B0002'>B0002</option><option value='B0003'>B0003</option><option value='B0004'>B0004</option><option value='B0005'>B0005</option><option value='B0006'>B0006</option><option value='B0007'>B0007</option><option value='B0008'>B0008</option><option value='B0009'>B0009</option><option value='B0010'>B0010</option><option value='B0011'>B0011</option><option value='B0012'>B0012</option><option value='B0013'>B0013</option><option value='B0014'>B0014</option><option value='B0015'>B0015</option><option value='B0016'>B0016</option><option value='B0017'>B0017</option><option value='B0018'>B0018</option><option value='B0019'>B0019</option><option value='B0020'>B0020</option>                                      
                              </select>
                            <input type="submit" name="submit" value="Remove Book" style="width:auto;">
                            </form>

提前感谢您的帮助!

Answer 1

尝试打印并查看是否获得了所选的图书 ID。每当您在查询中遇到问题时，请打印并查看。

添加此行

print "DELETE FROM books WHERE book_id=$books";

之前

$result=mysql_query("DELETE FROM books WHERE book_id=$books");

我认为您没有收到格式正确的图书 ID。

换行

 echo "<option value=\"".$book_id."\">".$book_id."</option>";

作为

 echo "<option value='".$book_id."'>".$book_id."</option>";

并且还使用单引号来封装一个值。改变

 $result=mysql_query("DELETE FROM books WHERE book_id=$books");

至

 $result=mysql_query("DELETE FROM books WHERE book_id='".$books."'");