如何在PHP中操作XML文件？通过SimpleXML解析和生成XML

// 从字符串解析
$xmlString = '<bookstore><book category="cooking"><title lang="en">Everyday Italian</title><author>Giada De Laurentiis</author><year>2005</year><price>30.00</price></book></bookstore>';
$xml = simplexml_load_string($xmlString);

if ($xml === false) {
    echo "解析XML字符串失败。\n";
    foreach(libxml_get_errors() as $error) {
        echo "\t", $error->message;
    }
    exit;
}

// 从文件解析
// 假设你有一个名为 'books.xml' 的文件
// $xml = simplexml_load_file('books.xml');
// if ($xml === false) { /* 错误处理同上 */ }

// 访问元素
echo "书名: " . $xml->book->title . "\n"; // 输出: 书名: Everyday Italian

// 访问属性
echo "类别: " . $xml->book['category'] . "\n"; // 输出: 类别: cooking
echo "标题语言: " . $xml->book->title['lang'] . "\n"; // 输出: 标题语言: en

// 遍历多个同名元素
$xmlMultipleBooks = '<bookstore><book><title>Book A</title></book><book><title>Book B</title></book></bookstore>';
$books = simplexml_load_string($xmlMultipleBooks);
foreach ($books->book as $book) {
    echo "遍历到的书名: " . $book->title . "\n";
}

// 创建一个新的SimpleXMLElement对象
$newXml = new SimpleXMLElement('<root/>');

// 添加子元素
$user = $newXml->addChild('user');
$user->addChild('id', '123');
$user->addChild('name', 'Alice');
$user->addChild('email', 'alice@example.com');

// 添加属性
$user->addAttribute('status', 'active');
$user->email->addAttribute('verified', 'true');

// 添加另一个子元素，并直接设置值和属性
$product = $newXml->addChild('product', 'Laptop');
$product->addAttribute('sku', 'LP001');
$product->addAttribute('price', '1200.00');

// 输出生成的XML
echo $newXml->asXML();

/*
输出示例:
<?xml version="1.0"?>
<root>
    <user status="active">
        <id>123</id>
        <name>Alice</name>
        <email verified="true">alice@example.com</email>
    </user>
    <product sku="LP001" price="1200.00">Laptop</product>
</root>
*/

// 将XML保存到文件
// $newXml->asXML('new_data.xml');

$complexXmlString = <<<XML
<library>
    <book id="bk101">
        <author>Gambardella, Matthew</author>
        <title>XML Developer's Guide</title>
        <genre>Computer</genre>
        <price>44.95</price>
        <publish_date>2000-10-01</publish_date>
        <description>An in-depth look at creating applications with XML.</description>
    </book>
    <book id="bk102">
        <author>Ralls, Kim</author>
        <title>Midnight Rain</title>
        <genre>Fantasy</genre>
        <price>5.95</price>
        <publish_date>2000-12-16</publish_date>
        <description>A former architect battles an evil sorceress.</description>
    </book>
    <magazine id="mg001">
        <title>PHP Monthly</title>
        <issue>January 2023</issue>
    </magazine>
</library>
XML;

$library = simplexml_load_string($complexXmlString);
if ($library === false) {
    echo "解析复杂XML失败。\n";
    exit;
}

// 查找所有书的标题
echo "所有书的标题:\n";
$bookTitles = $library->xpath('//book/title');
foreach ($bookTitles as $title) {
    echo "- " . $title . "\n";
}

// 查找价格低于10元的书
echo "\n价格低于10元的书:\n";
$cheapBooks = $library->xpath('//book[price < 10]');
foreach ($cheapBooks as $book) {
    echo "- " . $book->title . " (价格: " . $book->price . ")\n";
}

// 查找ID为"bk101"的书的作者
echo "\nID为bk101的书的作者:\n";
$authorOfBk101 = $library->xpath('//book[@id="bk101"]/author');
if (!empty($authorOfBk101)) {
    echo "- " . $authorOfBk101[0] . "\n";
}

// 查找所有出版日期在2000年之后的图书
echo "\n2000年之后出版的图书:\n";
$booksAfter2000 = $library->xpath('//book[substring(publish_date, 1, 4) > "2000"]');
foreach ($booksAfter2000 as $book) {
    echo "- " . $book->title . " (出版日期: " . $book->publish_date . ")\n";
}

//

@

[]

delete()

$xmlString = '<config><settings><debug>true</debug><log_level>info</log_level></settings></config>';
$config = simplexml_load_string($xmlString);

if ($config === false) { /* 错误处理 */ exit; }

// 修改元素值
$config->settings->debug = 'false';
$config->settings->log_level = 'warning';

// 添加新属性
$config->settings->addAttribute('updated_at', date('Y-m-d H:i:s'));

// 修改现有属性
$config->settings['updated_at'] = '2023-10-27 10:30:00'; // 覆盖旧值

echo "修改后的XML:\n" . $config->asXML();

addChild()

addAttribute()

// 假设我们继续使用上面的 $config 对象
$newFeature = $config->addChild('feature');
$newFeature->addChild('name', 'Caching');
$newFeature->addChild('enabled', 'true');
$newFeature->addAttribute('version', '1.0');

echo "\n添加新元素后的XML:\n" . $config->asXML();

deleteChild()

unset()

// 假设我们想删除 <config><settings><debug> 元素
unset($config->settings->debug);

// 如果要删除具有特定属性的元素，可以结合XPath
$xmlWithMultipleItems = '<data><item id="1"/><item id="2"/><item id="3"/></data>';
$data = simplexml_load_string($xmlWithMultipleItems);

// 找到id为2的item
$itemToDelete = $data->xpath('//item[@id="2"]');
if (!empty($itemToDelete)) {
    // unset只能作用于SimpleXMLElement对象，不能直接作用于XPath返回的数组元素
    // 需要找到其在父节点中的索引，或者直接unset该对象
    // 简单粗暴的方式是：如果它是数组的第一个元素，直接unset
    // 但更稳妥的做法是找到其父节点，然后通过unset父节点的子元素
    $dom = dom_import_simplexml($itemToDelete[0]);
    $dom->parentNode->removeChild($dom);
    $data = simplexml_load_string($data->asXML()); // 重新加载以反映DOM修改
}


echo "\n删除debug元素后的XML:\n" . $config->asXML();
echo "\n删除id为2的item后的XML:\n" . $data->asXML();

unset()

simplexml_import_dom()

dom_import_simplexml()