Php 从Ajax原型检索XML数据

在一个PHP文件中，我解析来自数据库聊天的数据，以XML格式回送所有数据。然后，在index.php文件中，如果单击一个按钮，我将执行一个ajax请求以从XML检索数据。为什么我会失败？将数据从query.php文件回显到index.php文件是否正确

#connect to database
$servername = "localhost";
$username = "root";
$password = "root";
$db_name = "Concerts";

try
{
    $db = new PDO("mysql: host=$servername; dbname=$db_name", $username, $password);
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $e)
{
    echo "Connection failed: " . $e->getMessage();
    die;
}



$result = $db->query("SELECT * FROM events");


echo '<?xml version="1.0" encoding="UTF-8"?>
<event>';

foreach ($result as $row)
{
    echo "<title>" . $row['title'] . "</title>";
    echo "<details>" . $row['details'] . "</details>";
    echo "<date>" . $row['date'] . "</date>";
    echo "<place>" . $row['place'] . "</place>";
}

echo "</event>";
?>

query.php

#connect to database
$servername = "localhost";
$username = "root";
$password = "root";
$db_name = "Concerts";

try
{
    $db = new PDO("mysql: host=$servername; dbname=$db_name", $username, $password);
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $e)
{
    echo "Connection failed: " . $e->getMessage();
    die;
}



$result = $db->query("SELECT * FROM events");


echo '<?xml version="1.0" encoding="UTF-8"?>
<event>';

foreach ($result as $row)
{
    echo "<title>" . $row['title'] . "</title>";
    echo "<details>" . $row['details'] . "</details>";
    echo "<date>" . $row['date'] . "</date>";
    echo "<place>" . $row['place'] . "</place>";
}

echo "</event>";
?>

index.php

---

PHP可以自己工作吗$result从未使用过，$event也没有定义。尝试学习如何使用SimpleXML来构建XML内容，这比使用自己动手的方法更安全。最好使用json而不是XML。使用SimpleXML我无法构建字符串，我需要逐段构建它，首先放入介绍，然后用for循环填充它。。。这样做并不意味着SimpleXML被设计成能够动态构建数据——否则它几乎毫无用处。