PHP Australia Conference 2015

DOMXPath::evaluate

(PHP 5 >= 5.1.0)

DOMXPath::evaluate Evaluates the given XPath expression and returns a typed result if possible

Opis

public mixed DOMXPath::evaluate ( string $expression [, DOMNode $contextnode [, bool $registerNodeNS = true ]] )

Executes the given XPath expression and returns a typed result if possible.

Parametry

expression

The XPath expression to execute.

contextnode

The optional contextnode can be specified for doing relative XPath queries. By default, the queries are relative to the root element.

registerNodeNS

The optional registerNodeNS can be specified to disable automatic registration of the context node.

Zwracane wartości

Returns a typed result if possible or a DOMNodeList containing all nodes matching the given XPath expression.

If the expression is malformed or the contextnode is invalid, DOMXPath::evaluate() returns FALSE.

Rejestr zmian

Wersja Opis
5.3.3 The registerNodeNS parameter was added.

Przykłady

Przykład #1 Getting the count of all the english books

<?php

$doc 
= new DOMDocument;

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

$xpath = new DOMXPath($doc);

$tbody $doc->getElementsByTagName('tbody')->item(0);

// our query is relative to the tbody node
$query 'count(row/entry[. = "en"])';

$entries $xpath->evaluate($query$tbody);
echo 
"There are $entries english books\n";

?>

Powyższy przykład wyświetli:

There are 2 english books

Zobacz też:

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User Contributed Notes 4 notes

up
1
daniel at danielnorton dot com
3 years ago
Note that this method does not provide any means to distinguish between a successful result that returns FALSE and an error.

For example, this will succeed and return FALSE:

<?php $xpath->evaluate("1 = 0"); ?>

One workaround when you know you are expecting a Boolean is to wrap the result with string(). e.g.

<?php $xpath->evaluate("string(1 = 0)"); ?>

This will return a string "false" on success, or the Boolean FALSE on error.
up
1
Damien Bezborodov
3 years ago
If your expression returns a node set, you will get a DOMNodeList instead of a typed result. Instead, try modifying your expression from "//node[1]" to "string(//node[1])".
up
1
yuriucsal at NOSPAM dot yahoo dot com dot br
9 years ago
this class can substitute the method evaluate while it is not validated. Made for Yuri Bastos and Jo�o Gilberto Magalh�es.

<?php

   
class XPtahQuery
   
{
       
// function returns a DOMNodeList from a relative xPath
       
public static function selectNodes($pNode, $xPath)
        {

           
$pos = strpos(self::getFullXpath($pNode),"/",1);
           
$xPathQuery = substr(self::getFullXpath($pNode),$pos);//to paste  /#document[1]/
           
$xPathQueryFull = $xPathQuery. $xPath;
           
$domXPath = new DOMXPath($pNode->ownerDocument);
           
$rNodeList = $domXPath->query($xPathQueryFull);

                return
$rNodeList;
        }
       
// function returns a DOMNode from a xPath from other DOMNode
       
public static function selectSingleNode($pNode, $xPath)
        {

           
$pos = strpos(self::getFullXpath($pNode),"/",1);
           
$xPathQuery = substr(self::getFullXpath($pNode),$pos);//to paste  /#document[1]/
           
$xPathQueryFull = $xPathQuery. $xPath;
           
$domXPath = new DOMXPath($pNode->ownerDocument);
           
$rNode = $domXPath->query($xPathQueryFull)->item(0);

                return
$rNode;
        }
       
//utilitaries functions off selectSingleNode
       
private function getNodePos($pNode, $nodeName)
        {
            if(
$pNode == null)
                {
                        return
0;
            }
            else
            {
               
$var = 0;
                    if (
$pNode->previousSibling != null)
                    {
                    if (
$pNode->previousSibling->nodeName == $nodeName)
                    {
                       
$var = 1;
                    }
                    }
                    return
self::getNodePos($pNode->previousSibling, $nodeName) + $var;
            }
        }
       
//utilitaries functions off selectSingleNode
       
private function getFullXpath($pNode)
        {
            if(
$pNode == null)
                {
                        return
"";
            }
            else
            {

                return
self::getFullXpath($pNode->parentNode) . "/" . $pNode->nodeName . "[" .strval(self::getNodePos($pNode, $pNode->nodeName)+1) . "]";//+1 to get the real xPath index

           
}
        }
    }
?>
up
0
daniel ad demus dk
6 years ago
It seems this method is only included from PHP 5.1.
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