php教程

DOMNodeList::item

(PHP 5, PHP 7)

DOMNodeList::item — Retrieves a node specified by index

说明

DOMNodeList::item ( int $index ) : DOMNode

Retrieves a node specified by index within the DOMNodeList object.

Tip

If you need to know the number of nodes in the collection, use the length property of the DOMNodeList object.

参数

index

Index of the node into the collection.

返回值

The node at the indexth position in the DOMNodeList, or NULL if that is not a valid index.

范例

Example #1 Traversing all the entries of the table

<?php

$doc = new DOMDocument;
$doc->load('book.xml');

$items = $doc->getElementsByTagName('entry');

for ($i = 0; $i < $items->length; $i++) {
    echo $items->item($i)->nodeValue . "\n";
}

?>

Alternatively, you can use foreach, which is a much more convenient way:

<?php

foreach ($items as $item) {
    echo $item->nodeValue . "\n";
}

?>

以上例程会输出：

Title
Author
Language
ISBN
The Grapes of Wrath
John Steinbeck
en
0140186409
The Pearl
John Steinbeck
en
014017737X
Samarcande
Amine Maalouf
fr
2253051209

User Contributed Notes

jeffpuckett2 at gmail dot com 15-Jun-2016 02:55
DOMNodelist::item can return a DOMElement object, which extends DOMNode class. But it can also return a DOMText object.

<?php
$xml = '
<root>
  <node/>
  <node>
    <sub>more</sub>
  </node>
  <node>
    <sub>another</sub>
  </node>
  <node>value</node>
</root>
';

$doc = new DOMDocument();
$doc->loadXML($xml);

$items = $doc->documentElement->childNodes;
for ($i = 0; $i < $items->length; $i++)
  echo get_class($items->item($i)).PHP_EOL;
?>

Results in this output:

DOMText
DOMElement
DOMText
DOMElement
DOMText
DOMElement
DOMText
DOMElement
DOMText
Anonymous 25-Jun-2012 11:36
calling domnodelist->item($i) with an index $i greater than domnodelist->length - 1 , will return the entire document, will not produce an error, and will not circle back to the start of the list.
Nagy Attila 06-Jan-2011 09:02
DOMNodeList::item does not return in constant time!

If you need to iterate over large nodelist then you'd better use standard navigation.

Instead of:

<?php
foreach ($nodelist as $node) {
    // do something
}
?>

you could do:

<?php
$node = $parentnode->firstChild;

do {
    // do something
} while ($node = $node->nextSibling);
?>
olivier dot berger at it-sudparis dot eu 21-Aug-2008 02:56
It seems that with zend.ze1_compatibility_mode on, the only way to iterate over the items list is with :
for ($i = 0; $i < $nodeList->length; ++$i) {
    $nodeName = $nodeList->item($i)->nodeName;
    $nodeValue = $nodeList->item($i)->nodeValue;
}

As other attemps failed :

for ($i = 0; $i < $nodeList->length; ++$i) {
    $node = &$nodeList->item($i);
    $nodeName = $node->nodeName;
    $nodeValue = $node->nodeValue;
}

or :
foreach ($nodeList as $node) {
    echo $node->nodeName;
    echo $node->nodeValue;
}
vinyanov at poczta dot onet dot pl 05-Jan-2008 10:12
SimpleXML has its own SPL iterator. See http://www.php.net/~helly/php/ext/spl/classSimpleXMLIterator.html . But I guess that there are none for DOM nodes. By the way, two out of three implementations I found over the Net were not recursive, so I wrote my own. Here is the snippet:

<?php

class DOMNodeListIterator implements RecursiveIterator
{
    private
        $nodes,
        $offset;

    function __construct(DOMNodeList $nodes)
    {
        return $this -> nodes = $nodes;
    }
   
    function rewind()
    {
        return $this -> offset = 0;
    }
   
    function current()
    {
        return $this -> nodes -> item($this -> offset);
    }

    function key()
    {
        return $this -> current() -> nodeName;
    }
   
    function next()
    {
        return $this -> offset++;
    }
   
    function valid()
    {
        return $this -> offset < $this -> nodes -> length;
    }
   
    function hasChildren()
    {
        return isset($this -> current() -> childNodes -> length) && $this -> current() -> childNodes -> length > 0;
    }
   
    function getChildren()
    {
        return new self($this -> current() -> childNodes);
    }
}

?>

Remember to use RecursiveIteratorIterator::SELF_FIRST flag when you create your iterator iterator.

<?php

$iterator = new DOMNodeListIterator($document -> childNodes);
$iterator = new RecursiveIteratorIterator($iterator, RecursiveIteratorIterator::SELF_FIRST);

?>

Should work, has just few minutes though. :)
Hayley Watson 29-Oct-2007 02:14
Keep in mind that DOMNodelists are "live" - changes to the document or node that the DOMNodelist was derived from will be reflected in the DOMNodelist. In other words, a list of a parent node's children will change if you change the parent's children!
james dot dunmore at gmai dot com 27-Jul-2007 08:57
tfg_allardyce at gmail dot com

I have had exactly this problem.

To rectify I've had to do this:
<?php
$old_element = $doc->getElementsByTagName('Element1')->item(0);
$new_element = $doc->createElement('NewElement1');

$old_element_childNodes = $old_element->childNodes;
$length = $old_element_childNodes->length;

for($i = 0; $i < $length; $i++)
{       
    $oldChildren_array[] = $old_element_childNodes->item($i);
}

foreach($oldChildren_array as $old_c)
{
    $new_element->appendChild($old_c);
}
?>

Rather than this:
(which I will bug report)
<?php
$old_element = $doc->getElementsByTagName('Element1')->item(0):
$new_element = $doc->createElement('NewElement1');

foreach($old_element->childNode as $node)
{
     $new_element->appendChild($node);
}

?>

Using the latter, randomally removes the children!
Geoffrey Thubron 26-May-2007 02:47
@ tfg_allardyce at gmail dot com

You could loop through the list backwards, that way, you are only ever taking off the last item from the list, and hence wont have disrupted the order.
oliver dot christen at camptocamp dot com 13-Feb-2007 07:27
NodeList are something annoying because you can't output the content with a simple print_r, so I did a little function that add all the node to a new empty DOMDocument and output it as a string.
Have fun.

<?php

public function domNodeList_to_string($DomNodeList) {
    $output = '';
    $doc = new DOMDocument;
    while ( $node = $DomNodeList->item($i) ) {
        // import node
        $domNode = $doc->importNode($node, true);
        // append node
        $doc->appendChild($domNode);
        $i++;
    }
    $output = $doc->saveXML();
    $output = print_r($output, 1);
    // I added this because xml output and ajax do not like each others
    $output = htmlspecialchars($output);
    return $output;
}

?>

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