PHP扩展之XML操作（一）——SimpleXML
- 黄舟原创
- 2018-05-17 09:38:185246浏览
一、简介及安装
SimpleXML 扩展提供了一个非常简单和易于使用的工具集，能将 XML 转换成一个带有一般属性选择器和数组迭代器的对象。
此扩展需要 libxml PHP 扩展。这表示需要使用 --enable-libxml ，尽管这将隐式完成因为 libxml 是缺省开启的。
需要PHP5及以上版本。
此扩展默认为启用,编译时可通过下列选项禁用： --disable-simplexml
二、使用示例
基本使用
Example #1 Include file example.php with XML string
<?php $xmlstr = <<<XML <?xml version='1.0' standalone='yes'?> <movies> <movie> <title>PHP: Behind the Parser</title> <characters> <character> <name>Ms. Coder</name> <actor>Onlivia Actora</actor> </character> <character> <name>Mr. Coder</name> <actor>El ActÓr</actor> </character> </characters> <plot> So, this language. It's like, a programming language. Or is it a scripting language? All is revealed in this thrilling horror spoof of a documentary. </plot> <great-lines> <line>PHP solves all my web problems</line> </great-lines> <rating type="thumbs">7</rating> <rating type="stars">5</rating> </movie> </movies> XML; ?>
The simplicity of SimpleXML appears most clearly when one extracts a string or number from a basic XML document.
Example #2 Getting a82a54010e8e844b28dec6f52c796df1
<?phpinclude 'example.php'; $movies = new SimpleXMLElement($xmlstr); echo $movies->movie[0]->plot;?>
以上例程会输出：
So, this language. It's like, a programming language. Or is it a scripting language? All is revealed in this thrilling horror spoof of a documentary.
Accessing elements within an XML document that contain characters not permitted under PHP's naming convention (e.g. the hyphen) can be accomplished by encapsulating the element name within braces and the apostrophe.
Example #3 Getting 15a73cc5312745b1b00671f6e690e36a
<?phpinclude 'example.php';
$movies = new SimpleXMLElement($xmlstr);
echo $movies->movie->{'great-lines'}->line;?>以上例程会输出：
PHP solves all my web problems
Example #4 Accessing non-unique elements in SimpleXML
When multiple instances of an element exist as children of a single parent element, normal iteration techniques apply.
<?phpinclude 'example.php';
$movies = new SimpleXMLElement($xmlstr);
/* For each <character> node, we echo a separate <name>. */foreach ($movies->movie->characters->character as $character) {
echo $character->name, ' played by ', $character->actor, PHP_EOL;}
?>以上例程会输出：
Ms. Coder played by Onlivia Actora Mr. Coder played by El ActÓr
Note:
Properties ($movies->movie in previous example) are not arrays. They are iterable and accessible objects.
Example #5 Using attributes
So far, we have only covered the work of reading element names and their values. SimpleXML can also access element attributes. Access attributes of an element just as you would elements of an array.
<?phpinclude 'example.php';
$movies = new SimpleXMLElement($xmlstr);
/* Access the <rating> nodes of the first movie.* Output the rating scale, too. */
foreach ($movies->movie[0]->rating as $rating) {
switch((string) $rating['type']) { // Get attributes as element indicescase 'thumbs':echo $rating, ' thumbs up';
break;case 'stars':echo $rating, ' stars';break;}}
?>以上例程会输出：
7 thumbs up5 stars
Example #6 Comparing Elements and Attributes with Text
To compare an element or attribute with a string or pass it into a function that requires a string, you must cast it to a string using (string). Otherwise, PHP treats the element as an object.
<?phpinclude 'example.php';
$movies = new SimpleXMLElement($xmlstr);
if ((string) $movies->movie->title == 'PHP: Behind the Parser') {print 'My favorite movie.';}
echo htmlentities((string) $movies->movie->title);?>以上例程会输出：
My favorite movie.PHP: Behind the Parser
Example #7 Comparing Two Elements
Two SimpleXMLElements are considered different even if they point to the same element since PHP 5.2.0.
<?phpinclude 'example.php'; $movies1 = new SimpleXMLElement($xmlstr);$movies2 = new SimpleXMLElement($xmlstr); var_dump($movies1 == $movies2); // false since PHP 5.2.0?>
以上例程会输出：
bool(false)
Example #8 Using XPath
SimpleXML includes built-in support. To find all db0c08544b71179f3fd0e855bd613a1b elements:
<?phpinclude 'example.php';
$movies = new SimpleXMLElement($xmlstr);
foreach ($movies->xpath('//character') as $character) {
echo $character->name, 'played by ', $character->actor, PHP_EOL;}?>'//' serves as a wildcard. To specify absolute paths, omit one of the slashes.
以上例程会输出：
Ms. Coder played by Onlivia Actora Mr. Coder played by El ActÓr
Example #9 Setting values
Data in SimpleXML doesn't have to be constant. The object allows for manipulation of all of its elements.
<?phpinclude 'example.php';$movies = new SimpleXMLElement($xmlstr); $movies->movie[0]->characters->character[0]->name = 'Miss Coder'; echo $movies->asXML();?>
以上例程会输出：
3e5184b51d19bd3b3173071244ff71fe eab6e99f51fee68293d1126fa516c747 8adf8e6c41d19c74d254355bd9d9c69e b2386ffb911b14667cb8f0f91ea547a7PHP: Behind the Parser6e916e0f7d1e588d4f442bf645aedb2f c3ae6056e653b437c6b27357b7e7671a db0c08544b71179f3fd0e855bd613a1b 8a11bc632ea32a57b3e3693c7987c420Miss Coderdf406f776eecbaf16b62325323196f14 194eaccae6455d5c407b1ac2afe04cd0Onlivia Actorac0d1bcc4fa4e9e034ebc23e1ef89e5c2 66707054a46c2dec1bf24d9318ba1124 db0c08544b71179f3fd0e855bd613a1b 8a11bc632ea32a57b3e3693c7987c420Mr. Coderdf406f776eecbaf16b62325323196f14 194eaccae6455d5c407b1ac2afe04cd0El ActÓrc0d1bcc4fa4e9e034ebc23e1ef89e5c2 66707054a46c2dec1bf24d9318ba1124 aabc3226380a602ad187eb87d5efa83f a82a54010e8e844b28dec6f52c796df1 So, this language. It's like, a programming language. Or is it a scripting language? All is revealed in this thrilling horror spoof of a documentary. fa8825681e04013deb51ef36ab6dbac6 54a9d3919a9de3703b391ab1e4eaee87 15a73cc5312745b1b00671f6e690e36aPHP solves all my web problems6e6d7ec7f2f63fbe473136c2c34a55b7 c0dd7eda886ba0d09f5a00454545474c e27af9d8c16e5d4022ce762c86f195be79df14055a92f49c29299ca2d367bde62 b724a65f9508b61211142b27c8620c4659df14055a92f49c29299ca2d367bde62 96664a6d22a82ab9c28a528afca408bc c3a75a871bc1ee80ecb54700c0759808
Example #10 Adding elements and attributes
Since PHP 5.1.3, SimpleXML has had the ability to easily add children and attributes.
<?phpinclude 'example.php';$movies = new SimpleXMLElement($xmlstr); $character = $movies->movie[0]->characters->addChild('character');$character->addChild('name', 'Mr. Parser'); $character->addChild('actor', 'John Doe'); $rating = $movies->movie[0]->addChild('rating', 'PG');$rating->addAttribute('type', 'mpaa'); echo $movies->asXML();?>
以上例程会输出：
3e5184b51d19bd3b3173071244ff71fe eab6e99f51fee68293d1126fa516c747 8adf8e6c41d19c74d254355bd9d9c69e b2386ffb911b14667cb8f0f91ea547a7PHP: Behind the Parser6e916e0f7d1e588d4f442bf645aedb2f c3ae6056e653b437c6b27357b7e7671a db0c08544b71179f3fd0e855bd613a1b 8a11bc632ea32a57b3e3693c7987c420Ms. Coderdf406f776eecbaf16b62325323196f14 194eaccae6455d5c407b1ac2afe04cd0Onlivia Actorac0d1bcc4fa4e9e034ebc23e1ef89e5c2 66707054a46c2dec1bf24d9318ba1124 db0c08544b71179f3fd0e855bd613a1b 8a11bc632ea32a57b3e3693c7987c420Mr. Coderdf406f776eecbaf16b62325323196f14 194eaccae6455d5c407b1ac2afe04cd0El ActÓrc0d1bcc4fa4e9e034ebc23e1ef89e5c2 66707054a46c2dec1bf24d9318ba1124 db0c08544b71179f3fd0e855bd613a1b8a11bc632ea32a57b3e3693c7987c420Mr. Parserdf406f776eecbaf16b62325323196f14194eaccae6455d5c407b1ac2afe04cd0John Doec0d1bcc4fa4e9e034ebc23e1ef89e5c266707054a46c2dec1bf24d9318ba1124aabc3226380a602ad187eb87d5efa83f a82a54010e8e844b28dec6f52c796df1 So, this language. It's like, a programming language. Or is it a scripting language? All is revealed in this thrilling horror spoof of a documentary. fa8825681e04013deb51ef36ab6dbac6 54a9d3919a9de3703b391ab1e4eaee87 15a73cc5312745b1b00671f6e690e36aPHP solves all my web problems6e6d7ec7f2f63fbe473136c2c34a55b7 c0dd7eda886ba0d09f5a00454545474c e27af9d8c16e5d4022ce762c86f195be79df14055a92f49c29299ca2d367bde62 b724a65f9508b61211142b27c8620c4659df14055a92f49c29299ca2d367bde62 8f35ab349d6453d281f32443bf3504f4PG9df14055a92f49c29299ca2d367bde6296664a6d22a82ab9c28a528afca408bc c3a75a871bc1ee80ecb54700c0759808
Example #11 DOM Interoperability
PHP has a mechanism to convert XML nodes between SimpleXML and DOM formats. This example shows how one might change a DOM element to SimpleXML.
<?php$dom = new DOMDocument;$dom->loadXML('<books><book>
<title>blah</title></book></books>');if (!$dom) {echo 'Error while parsing the document';exit;}
$books = simplexml_import_dom($dom);
echo $books->book[0]->title;?>以上例程会输出：
blah
处理XML错误
Example #1 Loading broken XML string
<?php
libxml_use_internal_errors(true);
$sxe = simplexml_load_string("<?xml version='1.0'><broken><xml></broken>");
if ($sxe === false) {
echo "Failed loading XML\n";
foreach(libxml_get_errors() as $error) {
echo "\t", $error->message;
}
}
?>以上例程会输出：
Failed loading XML Blank needed here parsing XML declaration: '?>' expected Opening and ending tag mismatch: xml line 1 and broken Premature end of data in tag broken line 1
三、相关函数
simplexml_import_dom — Get a SimpleXMLElement object from a DOM node.
simplexml_load_file — Interprets an XML file into an object
simplexml_load_string — Interprets a string of XML into an object
四、相关类及成员函数
SimpleXMLElement类
SimpleXMLElement::addAttribute — Adds an attribute to the SimpleXML element
SimpleXMLElement::addChild — Adds a child element to the XML node
SimpleXMLElement::asXML — Return a well-formed XML string based on SimpleXML element
SimpleXMLElement::attributes — Identifies an element's attributes
SimpleXMLElement::children — Finds children of given node
SimpleXMLElement::__construct — Creates a new SimpleXMLElement object
SimpleXMLElement::count — Counts the children of an element
SimpleXMLElement::getDocNamespaces — Returns namespaces declared in document
SimpleXMLElement::getName — Gets the name of the XML element
SimpleXMLElement::getNamespaces — Returns namespaces used in document
SimpleXMLElement::registerXPathNamespace — Creates a prefix/ns context for the next XPath query
SimpleXMLElement::saveXML — 别名 SimpleXMLElement::asXML
SimpleXMLElement::__toString — Returns the string content
SimpleXMLElement::xpath — Runs XPath query on XML data
SimpleXMLIterator类
SimpleXMLIterator::current — Returns the current element
SimpleXMLIterator::getChildren — Returns the sub-elements of the current element
SimpleXMLIterator::hasChildren — Checks whether the current element has sub elements.
SimpleXMLIterator::key — Return current key
SimpleXMLIterator::next — Move to next element
SimpleXMLIterator::rewind — Rewind to the first element
SimpleXMLIterator::valid — Check whether the current element is valid
以上就是PHP扩展之XML操作（一）——SimpleXML的内容，更多相关内容请关注PHP中文网（www.php.cn）！