DOMDocument::getElementById
(PHP 5)
DOMDocument::getElementById — Searches for an element with a certain id
Description
This function is similar to DOMDocument::getElementsByTagName but searches for an element with a given id.
For this function to work, you will need either to set some ID attributes with DOMElement::setIdAttribute or a DTD which defines an attribute to be of type ID. In the later case, you will need to validate your document with DOMDocument::validate or DOMDocument::$validateOnParse before using this function.
Parameters
-
elementId -
The unique id value for an element.
Return Values
Returns the DOMElement or NULL if the element is
not found.
Examples
Example #1 DOMDocument::getElementById() Example
The following examples use book.xml which contains the following:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE books [
<!ELEMENT books (book+)>
<!ELEMENT book (title, author+, xhtml:blurb?)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT blurb (#PCDATA)>
<!ELEMENT author (#PCDATA)>
<!ATTLIST books xmlns CDATA #IMPLIED>
<!ATTLIST books xmlns:xhtml CDATA #IMPLIED>
<!ATTLIST book id ID #IMPLIED>
<!ATTLIST author email CDATA #IMPLIED>
]>
<?xml-stylesheet type="text/xsl" href="style.xsl"?>
<books xmlns="http://books.php/" xmlns:xhtml="http://www.w3.org/1999/xhtml">
<book id="php-basics">
<title>PHP Basics</title>
<author email="jim.smith@basics.php">Jim Smith</author>
<author email="jane.smith@basics.php">Jane Smith</author>
<xhtml:blurb><![CDATA[
<p><em>PHP Basics</em> provides an introduction to PHP.</p>
]]></xhtml:blurb>
</book>
<book id="php-advanced">
<title>PHP Advanced Programming</title>
<author email="jon.doe@advanced.php">Jon Doe</author>
</book>
</books>
<?php
$doc = new DomDocument;
// We need to validate our document before refering to the id
$doc->validateOnParse = true;
$doc->Load('book.xml');
echo "The element whose id is 'php-basics' is: " . $doc->getElementById('php-basics')->tagName . "\n";
?>
The above example will output:
The element whose id is 'php-basics' is: book
- PHP Руководство
- Функции по категориям
- Индекс функций
- Справочник функций
- Обработка XML
- Document Object Model
- Функция DOMDocument::__construct() - Создание нового DOMDocument объекта
- Функция DOMDocument::createAttribute() - Создает новый атрибут
- Функция DOMDocument::createAttributeNS() - Создает новый узел-атрибут с соответствующим ему пространством имен
- Функция DOMDocument::createCDATASection() - Создает новый cdata узел
- Функция DOMDocument::createComment() - Создает новый узел-комментарий
- Функция DOMDocument::createDocumentFragment() - Создание фрагмента докуента
- Функция DOMDocument::createElement() - Создает новый узел-элемент
- Функция DOMDocument::createElementNS() - Создание нового узла-элемента с соответствующим пространством имен
- Функция DOMDocument::createEntityReference() - Создание нового узла-ссылки на сущность
- Функция DOMDocument::createProcessingInstruction() - Создает новый PI-узел
- Функция DOMDocument::createTextNode() - Создает новый текстовый узел
- Функция DOMDocument::getElementById() - Ищет элемент с заданным id
- Функция DOMDocument::getElementsByTagName() - Ищет все элементы с заданным локальным именем
- Функция DOMDocument::getElementsByTagNameNS() - Ищет элементы с заданным именем в определенном пространстве имен
- Функция DOMDocument::importNode() - Импорт узла в текущий документ
- Функция DOMDocument::load() - Загрузка XML из файла
- Функция DOMDocument::loadHTML() - Загрузка HTML из строки
- Функция DOMDocument::loadHTMLFile() - Загрузка HTML из файла
- Функция DOMDocument::loadXML() - Загрузка XML из строки
- Функция DOMDocument::normalizeDocument() - Нормализует документ
- Функция DOMDocument::registerNodeClass() - Регистрация расширенного класса, используемого для создания базового типа узлов
- Функция DOMDocument::relaxNGValidate() - Производит проверку документа на правильность построения посредством relaxNG
- Функция DOMDocument::relaxNGValidateSource() - Проверяет документ посредством relaxNG
- Функция DOMDocument::save() - Сохраняет XML дерево из внутреннего представления в файл
- DOMDocument::saveHTML
- DOMDocument::saveHTMLFile
- Функция DOMDocument::saveXML() - Сохраняет XML дерево из внутреннего представления в виде строки
- Функция DOMDocument::schemaValidate() - Проверяет действительности документа, основываясь на заданной схеме
- Функция DOMDocument::schemaValidateSource() - Проверяет действительность документа, основываясь на схеме
- Функция DOMDocument::validate() - Проверяет документ на соответствие его DTD
- Функция DOMDocument::xinclude() - Проводит вставку XInclude разделов в объектах DOMDocument
Коментарии
It seems getElementById works fine without setting validateOnParse to true. Which is nice since setting this to true caused some performance problems with my script.If you're trying to use getElementById with a xml file validated on a xsd file you must first use the schemaValidate function or getElementById will return null
Example:
$dom = new DomDocument();
$dom->load("users.xml");
$dom->schemaValidate("users.xsd");
$curruser = $dom->getElementById($user->name);
Validating a document from a DTD so as to use getElementById is sometimes impossible (for example when the head and body elements are not included yet in a XHtml document : the validation failed).Fortunately, xml:id is supported by this function :)
That may be useful.
http://www.w3.org/TR/xml-id/
If your XML document does not have a DTD that defines the "id" attribute as an ID, then the easiest thing to do is to use XPath->query() to find an element that matches "//[@id='x']"SAVE YOURSELF A MAJOR HEADACHE AND A LOT OF SEARCHING THROUGH DOCUMENTATION -
Instead of using $object->setAttribute('id', 'id_name_here')
USE THIS: $object->setAttribute('xml:id', 'id_name_here')
Then, to get the node value: $domDocumentObject->getElementById('id_name_here');
The xml:id attribute should AUTOMATICALLY be defined!!
Woohoo! That was easy......
You don't want to use "xml:id" ?
Here is the relaxNG trick (with a generic schema):
(tested with libxml 2.6.26)
<?php
$doc = new DOMDocument();
$doc->load(...);
$rng = '
<grammar xmlns="http://relaxng.org/ns/structure/1.0" datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
<start>
<element>
<anyName/>
<ref name="anythingID"/>
</element>
</start>
<define name="anythingID">
<zeroOrMore>
<choice>
<element>
<anyName/>
<ref name="anythingID"/>
</element>
<attribute name="id">
<data type="ID"/>
</attribute>
<zeroOrMore>
<attribute><anyName/></attribute>
</zeroOrMore>
<text/>
</choice>
</zeroOrMore>
</define>
</grammar>
';
$doc->relaxNGValidateSource($rng);
var_dump($doc->getElementById('id1'));
?>
Note that ID values must be valid ones :
- integers do no work!
- @see http://www.w3.org/TR/REC-xml/#id
- => (Letter | '_' | ':') ( Letter | Digit | '.' | '-' | '_' | ':' | CombiningChar | Extender )*
From my experience, getElementById seem to work fine without any setups if you have loaded a HTML document. But in order for getElementById to work with a simple XML document that you've "constructed", you have to set up the id with "xml:" prefix and use setIdAttribute on the element you created or it won't work. See following example, hope this will save someone's frustration. If you have loaded the xml file, then all you have to make sure is the ID has a xml: prefix for the attribute. But if you start to append the XML document, don't forget to setIdAttribute on the id name or those elements or getElementById will return null when you try to find them.
<?php
/* test.xml
<?xml version="1.0" encoding="utf-8"?>
<root>
<child xml:id="id_xxxxxx" status="partial">
<sub_child>Some Data</sub_child>
</child>
</root>
*/
$xmlDom = new DOMDocument('1.0', 'utf-8');
$xmlDom->formatOutput = true; // we want a nice output
// create a root
$eltRoot = $xmlDom->createElement("root");
$xmlDom->appendChild($eltRoot);
$eltChild = $xmlDom->createElement("child");
$eltRoot->appendChild($eltChild);
// add a id attribute
$attr = $xmlDom->createAttribute("xml:id"); // needs xml prefix or getElementById won't work
$eltChild->appendChild($attr);
/// create the text node and append to the created element
$tNode = $xmlDom->createTextNode("id_8120528");
$attr->appendChild($tNode);
$eltChild->setIdAttribute("xml:id", true); // VERY IMPORT or getElementById won't work
// add a id attribute
$attr = $xmlDom->createAttribute("status");
$eltChild->appendChild($attr);
/// create the text node and append to the created element
$tNode = $xmlDom->createTextNode("partial");
$attr->appendChild($tNode);
// add a subchild
$eltSub = $xmlDom->createElement("sub_child");
$eltChild->appendChild($eltSub);
$tNode = $xmlDom->createTextNode("Some Data");
$eltSub->appendChild($tNode);
$id = null;
$id = $xmlDom->getElementById("id_8120528");
assert ($id != null);
$strId = $id->getAttribute("xml:id"); // bug? empty
$strStatus = $id->getAttribute("status"); // this works!
assert ($id !=null);
$xmlDom->save("./_data/test.xml");
$xmlDom->load("./_data/test.xml"); // reloading fixes the problem
$nodeRoot = $xmlDom->getElementsByTagName("root");
if ($nodeRoot->length > 0) {
$eltRoot = $nodeRoot->item(0);
}
assert($eltRoot != null);
$id = null;
$id = $xmlDom->getElementById("id_8120528");
assert ($id != null);
$strId = $id->getAttribute("xml:id"); // this works now!
$strStatus = $id->getAttribute("status"); // this works!
?>
Had some issues with getElementById() while searching for a specific element in a XHTML document.
I wrote a small function what was solving my problem:
<?php
function getElementById($id)
{
$xpath = new DOMXPath($this->domDocument);
return $xpath->query("//*[@id='$id']")->item(0);
}
?>
Please note that if your HTML does not contain a doctype declaration, then getElementById will always return null.To set a hidden id that can be used by $dom->getElementById() apply setAttribute('id', true) as in the following example
$createItemNode = function ($data) use ($dom) {
$node = $dom->createElement("Item");
$node->setAttribute('id', $data->id);
$node->setAttribute('hed', $data->hed);
$node->setAttribute('run_time', $data->run_time);
$node->setAttribute('date', $data->date);
// Internally mark the id as 'xml:id' for getElementById to work. Adding xml:id manually to the tag will cause loadXML to throw an error DOMDocument: xml:id is not a NCName in Entity
$node->setIdAttribute('id', true);
return $node;
};
With $node->setIdAttribute('id', true), $dom->getElementById($id) will work
When you do $dom->saveXML(), the final doc will not contain any xml:id attribute.