There is a common "trick" often proposed to convert a SimpleXML object to an array, by running it through json_encode() and then json_decode(). I'd like to explain why this is a bad idea.
Most simply, because the whole point of SimpleXML is to be easier to use and more powerful than a plain array. For instance, you can write <?php $foo->bar->baz['bing'] ?> and it means the same thing as <?php $foo->bar[0]->baz[0]['bing'] ?>, regardless of how many bar or baz elements there are in the XML; and if you write <?php (string)$foo->bar[0]->baz[0] ?> you get all the string content of that node - including CDATA sections - regardless of whether it also has child elements or attributes. You also have access to namespace information, the ability to make simple edits to the XML, and even the ability to "import" into a DOM object, for much more powerful manipulation. All of this is lost by turning the object into an array rather than reading understanding the examples on this page.
Additionally, because it is not designed for this purpose, the conversion to JSON and back will actually lose information in some situations. For instance, any elements or attributes in a namespace will simply be discarded, and any text content will be discarded if an element also has children or attributes. Sometimes, this won't matter, but if you get in the habit of converting everything to arrays, it's going to sting you eventually.
Of course, you could write a smarter conversion, which didn't have these limitations, but at that point, you are getting no value out of SimpleXML at all, and should just use the lower level XML Parser functions, or the XMLReader class, to create your structure. You still won't have the extra convenience functionality of SimpleXML, but that's your loss.
基本的な SimpleXML の使用法
このリファレンスの多くの例では XML 文字列が必要です。それぞれの例で この文字列をくり返す代わりに、あるファイルにこの文字列を保存して、 例ごとに読みこむことにします。この読みこまれるファイルは、以下の例 に関するセクションで使います。 もしくは、XMLドキュメントを作成し、 simplexml_load_file() により読みこむことも 可能です。
例1 XML 文字列を設定するインクルードファイル example.php
<?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;
?>SimpleXML の容易さが最も明確に現われるのは、 簡単な XML ドキュメントから文字列または数字を展開する時です。
例2 <plot> を取得する
<?php
include 'example.php';
$movies = new SimpleXMLElement($xmlstr);
echo $movies->movie[0]->plot;
?>上の例の出力は以下となります。
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.
XML ドキュメント内の要素のうち、PHP の命名規約で許可されていない文字 (たとえばハイフンなど) を含む名前のものにアクセスするには、 要素名を括弧とアポストロフィで囲みます。
例3 <line> を取得する
<?php
include 'example.php';
$movies = new SimpleXMLElement($xmlstr);
echo $movies->movie->{'great-lines'}->line;
?>上の例の出力は以下となります。
PHP solves all my web problems
例4 SimpleXML でユニークでない要素にアクセスする
単一の親要素の子要素としてある要素のインスタンスが複数存在する時、 通常の反復処理を適用することができます。
<?php
include 'example.php';
$movies = new SimpleXMLElement($xmlstr);
/* 個々の <character> ノードに対して、<name> を分割して表示します */
foreach ($movies->movie->characters->character as $character) {
echo $character->name, ' played by ', $character->actor, PHP_EOL;
}
?>上の例の出力は以下となります。
Ms. Coder played by Onlivia Actora Mr. Coder played by El ActÓr
注意:
プロパティ (先ほどの例の
$movies->movie) は配列ではありません。反復処理 と 配列形式でのアクセス ができるオブジェクトです。
例5 属性を使用する
ここまでは、要素の名前と値を読む方法のみを扱って来ました。 SimpleXML は要素の属性にアクセスすることも可能です。 要素の属性にアクセスする方法は、配列 の要素に アクセスするのと全く同じです。
<?php
include 'example.php';
$movies = new SimpleXMLElement($xmlstr);
/* 最初の映画の <rating> ノードにアクセスします。
* また、その評価も出力します。*/
foreach ($movies->movie[0]->rating as $rating) {
switch((string) $rating['type']) { // 要素のインデックスとして、属性を取得します
case 'thumbs':
echo $rating, ' thumbs up';
break;
case 'stars':
echo $rating, ' stars';
break;
}
}
?>上の例の出力は以下となります。
7 thumbs up5 stars
例6 要素および属性をテキストと比較する
要素または属性を文字列と比較する、もしくは、文字列を引数とする関数に
渡すには、(string) により文字列にキャストする
必要があります。さもないと、PHP はこの要素をオブジェクトとして扱います。
<?php
include '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);
?>上の例の出力は以下となります。
My favorite movie.PHP: Behind the Parser
例7 ふたつの要素の比較
たとえ同一の要素を指していたとしても 2 つの SimpleXMLElements は異なるものと見なされます。
<?php
include 'example.php';
$movies1 = new SimpleXMLElement($xmlstr);
$movies2 = new SimpleXMLElement($xmlstr);
var_dump($movies1 == $movies2);
?>上の例の出力は以下となります。
bool(false)
例8 XPath の使用
SimpleXML は、XPath を標準でサポートしています。
<character> 要素をすべて見つけるには、
以下のようにします。
<?php
include 'example.php';
$movies = new SimpleXMLElement($xmlstr);
foreach ($movies->xpath('//character') as $character) {
echo $character->name, ' played by ', $character->actor, PHP_EOL;
}
?>
'//' はワイルドカードとして動作します。絶対パスを指定するには、
スラッシュを一つだけにします。
上の例の出力は以下となります。
Ms. Coder played by Onlivia Actora Mr. Coder played by El ActÓr
例9 値を設定する
SimpleXMLの中のデータは、定数とすることができません。 オブジェクトは、その全ての要素について変更が可能です。
<?php
include 'example.php';
$movies = new SimpleXMLElement($xmlstr);
$movies->movie[0]->characters->character[0]->name = 'Miss Coder';
echo $movies->asXML();
?>上の例の出力は以下となります。
<?xml version="1.0" standalone="yes"?>
<movies>
<movie>
<title>PHP: Behind the Parser</title>
<characters>
<character>
<name>Miss 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>
例10 要素と属性を追加する
SimpleXML を使用して簡単に子要素および属性を追加することができます。
<?php
include '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();
?>上の例の出力は以下となります。
<?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>
<character><name>Mr. Parser</name><actor>John Doe</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>
<rating type="mpaa">PG</rating></movie>
</movies>
例11 DOM との相互運用性
PHP は、SimpleXML 形式と DOM 形式の間で XML ノードを変換する機構を有しています。 この例では、DOM 要素を SimpleXML に変換することができます。
<?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;
?>上の例の出力は以下となります。
blah
add a note
User Contributed Notes 10 notes
rowan dot collins at gmail dot com ¶
9 years ago
jishcem at gmail dot com ¶
11 years ago
For me it was easier to use arrays than objects,
So, I used this code,
$xml = simplexml_load_file('xml_file.xml');
$json_string = json_encode($xml);
$result_array = json_decode($json_string, TRUE);
Hope it would help someone
Anonymous ¶
7 years ago
If your xml string contains booleans encoded with "0" and "1", you will run into problems when you cast the element directly to bool:
$xmlstr = <<<XML
<?xml version='1.0' standalone='yes'?>
<values>
<truevalue>1</truevalue>
<falsevalue>0</falsevalue>
</values>
XML;
$values = new SimpleXMLElement($xmlstr);
$truevalue = (bool)$values->truevalue; // true
$falsevalue = (bool)$values->falsevalue; // also true!!!
Instead you need to cast to string or int first:
$truevalue = (bool)(int)$values->truevalue; // true
$falsevalue = (bool)(int)$values->falsevalue; // false
gkokmdam at zonnet dot nl ¶
13 years ago
A quick tip on xpath queries and default namespaces. It looks like the XML-system behind SimpleXML has the same workings as I believe the XML-system .NET uses: when one needs to address something in the default namespace, one will have to declare the namespace using registerXPathNamespace and then use its prefix to address the otherwise in the default namespace living element.
<?php
$string = <<<XML
<?xml version='1.0'?>
<document xmlns="http://www.w3.org/2005/Atom">
<title>Forty What?</title>
<from>Joe</from>
<to>Jane</to>
<body>
I know that's the answer -- but what's the question?
</body>
</document>
XML;
$xml = simplexml_load_string($string);
$xml->registerXPathNamespace("def", "http://www.w3.org/2005/Atom");
$nodes = $xml->xpath("//def:document/def:title");
?>
ie dot raymond at gmail dot com ¶
14 years ago
If you need to output valid xml in your response, don't forget to set your header content type to xml in addition to echoing out the result of asXML():
<?php
$xml=simplexml_load_file('...');
...
...xml stuff
...
//output xml in your response:
header('Content-Type: text/xml');
echo $xml->asXML();
?>
kdos ¶
13 years ago
Using stuff like: is_object($xml->module->admin) to check if there actually is a node called "admin", doesn't seem to work as expected, since simplexml always returns an object- in that case an empty one - even if a particular node does not exist.
For me good old empty() function seems to work just fine in such cases.
Cheers
Max K. ¶
14 years ago
From the README file:
SimpleXML is meant to be an easy way to access XML data.
SimpleXML objects follow four basic rules:
1) properties denote element iterators
2) numeric indices denote elements
3) non numeric indices denote attributes
4) string conversion allows to access TEXT data
When iterating properties then the extension always iterates over
all nodes with that element name. Thus method children() must be
called to iterate over subnodes. But also doing the following:
foreach ($obj->node_name as $elem) {
// do something with $elem
}
always results in iteration of 'node_name' elements. So no further
check is needed to distinguish the number of nodes of that type.
When an elements TEXT data is being accessed through a property
then the result does not include the TEXT data of subelements.
Known issues
============
Due to engine problems it is currently not possible to access
a subelement by index 0: $object->property[0].
php at keith tyler dot com ¶
14 years ago
[Editor's Note: The SimpleXMLIterator class, however, does implement these methods.]
While SimpleXMLElement claims to be iterable, it does not seem to implement the standard Iterator interface functions like ::next and ::reset properly. Therefore while foreach() works, functions like next(), current(), or each() don't seem to work as you would expect -- the pointer never seems to move or keeps getting reset.
Josef ¶
3 years ago
How to find out if a Node exists:
<?xml version='1.0' standalone='yes'?>
<book>
<author>Josef</author>
<isbn></isbn>
</book>
empty($xml->isbn) will be true
isset($xml->isbn) will be true
empty($xml->title) will be true
isset($xml->title) will be false
radams at circlepix com ¶
15 years ago
To test whether an element exists:
<?php
$xml = <<<EOT
<?xml version='1.0' standalone='yes'?>
<root>
<test1></test1>
<test2 />
<test4> </test4>
</root>
EOT;
$xmlDoc = new SimpleXMLElement($xml);
echo "Test1: \n";
var_dump($xmlDoc->test1);
echo "\n(" . (bool)$xmlDoc->test1 . ")";
echo "\n\n";
echo "Test2: \n";
var_dump($xmlDoc->test2);
echo "\n(" . (bool)$xmlDoc->test2 . ")";
echo "\n\n";
echo "Test3: \n";
var_dump($xmlDoc->test3);
echo "\n(" . (bool)$xmlDoc->test3 . ")";
echo "\n\n";
echo "Test4: \n";
var_dump($xmlDoc->test4);
echo "\n(" . (bool)$xmlDoc->test4 . ")";
echo "\n\n";
?>
The var_dumps for test1, test2, and test3 are identical, but the (bool) test gives a '1' for test1 and test2, and a '' for test3.
