PHP读写XML文件的四种方法

PHP读写XML⽂件的四种⽅法
PHP对XML⽂件进⾏读写操作的⽅法⼀共有四种，分别是：字符串⽅式直接读写、DOMDocument读写、XMLWrite写和XMLReader读、SimpleXML读写，本⽂将依次对这四种⽅法进⾏介绍。

介绍之前⾸先对本⽂例⼦使⽤的数据和⽂件进⾏说明。

本⽂写XML⽂件的例⼦都是从MySQL中读取数据然后写⼊到XML⽂件中，读XML⽂件的例⼦都是从XML⽂件中读取数据后组装成数组的格式，数组中每个元素对应数据库中的⼀条记录。

MySQL中的数据：
XML⽂件：
<?xml version="1.0" encoding="utf8"?>
<studentcareer>
<period>
<starttime>2000</starttime>
<endtime>2002</endtime>
<school>培新⼩学</school>
</period>
<period>
<starttime>2002</starttime>
<endtime>2006</endtime>
<school>览表东阳学校</school>
</period>
<period>
<starttime>2006</starttime>
<endtime>2009</endtime>
<school>惠来慈云实验中学</school>
</period>
<period>
<starttime>2009</starttime>
<endtime>2012</endtime>
<school>惠来⼀中</school>
</period>
<period>
<starttime>2012</starttime>
<endtime>2016</endtime>
<school>华南师范⼤学</school>
</period>
</studentcareer>
读取XML⽂件后组装成的数据格式：
下⾯的例⼦使⽤的数据、⽂件都是以上所列数据、⽂件，介绍各个⽅法时不再赘述，直接贴代码。

⼀、PHP字符串⽅式读写XML⽂件：
1. 字符串⽅式写XML⽂件：
<?php
/**
* function：使⽤字符串⽅式写XML⽂件
* author：JetWu
* date：2016.12.03
**/
$mysqli = mysqli_connect('localhost', 'root', '123456', 'wjt');
if(mysqli_connect_errno()) die('database connect fail:' . mysqli_connect_error());
$sql = 'select * from study order by starttime';
$res = mysqli_query($mysqli, $sql);
$study = array();
while($row = mysqli_fetch_array($res)) {
$study[] = $row;
}
//XML标签配置
$xmlTag = array(
'starttime',
$str = "<studentcareer>\n";
foreach($study as $v) {
$str .= "\t<period>\n";
foreach($xmlTag as $x) {
$str .= "\t\t<".$x.">" . $v[$x] . "</".$x.">\n";
}
$str .= "\t</period>\n";
}
$str .= '</studentcareer>';
$file = './write_str.xml';
file_put_contents($file, $str);
2. 字符串⽅式读XML⽂件：
<?php
/**
* function：使⽤字符串⽅式读XML⽂件
* author：JetWu
* date：2016.12.03
**/
$file = './write_str.xml';
$con = file_get_contents($file);
//XML标签配置
$xmlTag = array(
'starttime',
'endtime',
'school'
);
$arr = array();
foreach($xmlTag as $x) {
preg_match_all("/<".$x.">.*<\/".$x.">/", $con, $temp);
$arr[] = $temp[0];
}
//去除XML标签并组装数据
$data = array();
foreach($arr as $key => $value) {
foreach($value as $k => $v) {
$a = explode($xmlTag[$key].'>', $v);
$v = substr($a[1], 0, strlen($a[1])-2);
$data[$k][$xmlTag[$key]] = $v;
}
}
echo '<pre>';
print_r($data);
⼆、DOMDocument读写XML⽂件
1. DOMDocument写XML⽂件：
<?php
/**
* function：DOMDocument写XML⽂件
* author：JetWu
* date：2016.12.03
**/
$mysqli = mysqli_connect('localhost', 'root', '123456', 'wjt');
if(mysqli_connect_errno()) die('database connect fail:' . mysqli_connect_error()); $sql = 'select * from study order by starttime';
$res = mysqli_query($mysqli, $sql);
$study = array();
while($row = mysqli_fetch_array($res)) {
$study[] = $row;
}
$dom = new DOMDocument('1.0', 'utf8');
$dom->formatOutput = true;
$studentcareer = $dom->createElement('studentcareer');
$dom->appendChild($studentcareer);
foreach($study as $s) {
$period = $dom->createElement('period');
$studentcareer->appendChild($period);
foreach($xmlTag as $x) {
$element = $dom->createElement($x);
$period->appendChild($element);
$text = $dom->createTextNode($s[$x]);
$element->appendChild($text);
}
}
$dom->save('./write_dom.xml');
2. DOMDocument读XML⽂件：
<?php
/**
* function：DOMDocument读XML⽂件
* author：JetWu
* date：2016.12.03
**/
//XML标签配置
$xmlTag = array(
'starttime',
'endtime',
'school'
);
$dom = new DOMDocument();
$dom->load('./write_dom.xml');
$periods = $dom->getElementsByTagName('period');
$study = array();
foreach($periods as $k => $p) {
foreach($xmlTag as $x) {
$node = $p->getElementsByTagName($x);
$study[$k][$x] = $node->item(0)->nodeValue;
}
}
echo '<pre>';
print_r($study);
三、XMLWriter和XMLReader读写XML⽂件
1. XMLWriter写XML⽂件：
<?php
/**
* function：XMLWriter写XML⽂件
* author：JetWu
* date：2016.12.03
**/
$mysqli = mysqli_connect('localhost', 'root', '123456', 'wjt');
if(mysqli_connect_errno()) die('database connect fail:' . mysqli_connect_error()); $sql = 'select * from study order by starttime';
$res = mysqli_query($mysqli, $sql);
$study = array();
while($row = mysqli_fetch_array($res)) {
$study[] = $row;
}
$xml = new XMLWriter();
$xml->openUri('./write_WR.xml');
$xml->setIndentString(' ');//设置缩进格式化使⽤的符号
$xml->setIndent(true);
$xml->startDocument('1.0', 'utf8');
$xml->startElement('studentcareer');
foreach($study as $s) {
$xml->startElement('period');
foreach($xmlTag as $x) {
$xml->startElement($x);
$xml->text($s[$x]);
$xml->endElement();
}
$xml->endElement();
}
$xml->endElement();
$xml->endDocument();
$xml->flush();
2. XMLReader读XML⽂件：
<?php
/**
* function：XMLReader读XML⽂件
* author：JetWu
* date：2016.12.03
**/
//XML标签配置
$xmlTag = array(
'starttime',
'endtime',
'school'
);
$xml = new XMLReader();
$xml->open('./write_WR.xml');
$study = array();
$count = 0;//记录数：⽅便组装数据
$name = '';
while($xml->read()) {
$n = $xml->name;
if($xml->nodeType == XMLReader::ELEMENT) {
if($n == 'period') {//开始下⼀条记录的读取
$count ++;
} else if(in_array($n, $xmlTag)) {//记录需要获取⽂本值的标签名 $name = $n;
}
} else if($xml->nodeType == XMLReader::TEXT) {
if(in_array($name, $xmlTag)) {
$study[$count][$name] = $xml->value;
}
}
}
$xml->close();
echo '<pre>';
print_r($study);
四、SimpleXML读写XML⽂件
1. SimpleXML写XML⽂件：
<?php
/**
* function：SimpleXML写XML⽂件
**/
$mysqli = mysqli_connect('localhost', 'root', '123456', 'wjt');
if(mysqli_connect_errno()) die('database connect fail:' . mysqli_connect_error());
$sql = 'select * from study order by starttime';
$res = mysqli_query($mysqli, $sql);
$study = array();
while($row = mysqli_fetch_array($res)) {
$study[] = $row;
}
//XML标签配置
$xmlTag = array(
'starttime',
'endtime',
'school'
);
$xml = new SimpleXMLElement('<?xml version="1.0" encoding="UTF-8"?><studentcareer />');
foreach($study as $s) {
$period = $xml->addChild('period');
foreach($xmlTag as $x) {
$period->addChild($x, $s[$x]);
}
}
$xml->asXml('./write_sim.xml');//输出XML⽂件（没有格式化）
2. SimpleXML读XML⽂件：
<?php
/**
* function：SimpleXML读XML⽂件
* author：JetWu
* date：2016.12.03
**/
//XML标签配置
$xmlTag = array(
'starttime',
'endtime',
'school'
);
$study = array();
$xml = simplexml_load_file('./write_sim.xml');
foreach($xml->children() as $period) {
$study[] = get_object_vars($period);//获取对象全部属性，返回数组
}
echo '<pre>';
print_r($study);
总结：这四种⽅法中，字符串的⽅式是最原始的⽅法。

SimpleXML和DOM扩展是属于基于树的解析器，把整个⽂档存储为树的数据结构中，需要把整个⽂档都加载到内存中才能⼯作，所以当处理⼤型XML⽂档的时候，性能会剧减。

XMLReader则是属于基于流的解析器，它不会⼀次把整个⽂档加载到内存中，⽽是每次分别读取其中的⼀个节点并允许实时与之交互，这种⽅式效率⾼，⽽且占内存少。