如何在PHP中使用XMLReader? [英] How to use XMLReader in PHP?

问题描述

我有以下XML文件，该文件很大，而且我无法获取simplexml来打开和读取该文件，因此我正在尝试XMLReader，但在php中没有成功

I have the following XML file, the file is rather large and i haven't been able to get simplexml to open and read the file so i'm trying XMLReader with no success in php

<?xml version="1.0" encoding="ISO-8859-1"?>
<products>
    <last_updated>2009-11-30 13:52:40</last_updated>
    <product>
        <element_1>foo</element_1>
        <element_2>foo</element_2>
        <element_3>foo</element_3>
        <element_4>foo</element_4>
    </product>
    <product>
        <element_1>bar</element_1>
        <element_2>bar</element_2>
        <element_3>bar</element_3>
        <element_4>bar</element_4>
    </product>
</products>

不幸的是，我还没有找到关于PHP的很好的教程，很想看看我如何才能将每个元素的内容存储在数据库中.

I've unfortunately not found a good tutorial on this for PHP and would love to see how I can get each element content to store in a database.

推荐答案

这都取决于工作单元的大小，但是我想您正在尝试连续对待每个<product/>节点.

It all depends on how big the unit of work, but I guess you're trying to treat each <product/> nodes in succession.

为此，最简单的方法是使用XMLReader到达每个节点，然后使用SimpleXML访问它们.这样，您可以将内存使用率保持在较低水平，因为您一次要处理一个节点，并且仍然可以利用SimpleXML的易用性.例如:

For that, the simplest way would be to use XMLReader to get to each node, then use SimpleXML to access them. This way, you keep the memory usage low because you're treating one node at a time and you still leverage SimpleXML's ease of use. For instance:

$z = new XMLReader;
$z->open('data.xml');

$doc = new DOMDocument;

// move to the first <product /> node
while ($z->read() && $z->name !== 'product');

// now that we're at the right depth, hop to the next <product/> until the end of the tree
while ($z->name === 'product')
{
    // either one should work
    //$node = new SimpleXMLElement($z->readOuterXML());
    $node = simplexml_import_dom($doc->importNode($z->expand(), true));

    // now you can use $node without going insane about parsing
    var_dump($node->element_1);

    // go to next <product />
    $z->next('product');
}

不同方法优缺点的简要概述:

Quick overview of pros and cons of different approaches:

仅XMLReader

• 优点:速度快，占用内存少

• Pros: fast, uses little memory

缺点:难以编写和调试，需要大量用户代码才能执行任何有用的操作.用户域代码很慢并且容易出错.另外，它为您提供了更多的代码行来维护

Cons: excessively hard to write and debug, requires lots of userland code to do anything useful. Userland code is slow and prone to error. Plus, it leaves you with more lines of code to maintain

XMLReader + SimpleXML

• 优点:不占用太多内存(仅处理一个节点所需的内存)，并且顾名思义，SimpleXML确实非常易于使用.

• Pros: doesn't use much memory (only the memory needed to process one node) and SimpleXML is, as the name implies, really easy to use.

缺点:为每个节点创建SimpleXMLElement对象不是很快.您确实必须对其进行基准测试，以了解它是否对您造成问题.不过，即使是一台普通的机器，也能够每秒处理一千个节点.

Cons: creating a SimpleXMLElement object for each node is not very fast. You really have to benchmark it to understand whether it's a problem for you. Even a modest machine would be able to process a thousand nodes per second, though.

XMLReader + DOM

• 优点:使用的内存与SimpleXML差不多，并且 XMLReader: :expand()比创建新的SimpleXMLElement更快.我希望可以使用simplexml_import_dom()，但在这种情况下似乎不起作用

• Pros: uses about as much memory as SimpleXML, and XMLReader::expand() is faster than creating a new SimpleXMLElement. I wish it was possible to use simplexml_import_dom() but it doesn't seem to work in that case

缺点:使用DOM很烦人.它位于XMLReader和SimpleXML之间.不像XMLReader那样复杂和尴尬，但是距离使用SimpleXML还很短.

Cons: DOM is annoying to work with. It's halfway between XMLReader and SimpleXML. Not as complicated and awkward as XMLReader, but light years away from working with SimpleXML.

我的建议:用SimpleXML编写一个原型，看看它是否对您有用.如果性能至关重要，请尝试使用DOM.尽可能远离XMLReader.请记住，编写的代码越多，引入错误或引入性能退化的可能性就越大.

My advice: write a prototype with SimpleXML, see if it works for you. If performance is paramount, try DOM. Stay as far away from XMLReader as possible. Remember that the more code you write, the higher the possibility of you introducing bugs or introducing performance regressions.

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