(PHP 5 >= 5.1.0, PHP 7)
DOMXPath::evaluate — Evaluates the given XPath expression and returns a typed result if possible
$expression
[, DOMNode $contextnode
[, bool $registerNodeNS = true
]] )
Executes the given XPath expression and returns
a typed result if possible.
expressionThe 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.
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.
| 版本 | 说明 |
|---|---|
| 5.3.3 |
The registerNodeNS parameter was added.
|
Example #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 $entries english books\n";
?>
以上例程会输出：
There are 2 english books
To query DOMNodes by their HTML classes, use such snippet
<?php
// CssClassXPathSelector
function ccxs($class) {
return '[contains(concat(" ", normalize-space(@class), " "), " ' . $class . ' ")]';
}
// then just
$domitems = $this->xpath("//*[@id='searchResultsRows']//a" . ccxs('listing_row'));
?>
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 $xpath->evaluate("string(1 = 0)"); ?>
This will return a string "false" on success, or the Boolean FALSE on error.
If your expression returns a node set, you will get a DOMNodeList instead of a typed result. Instead, try modifying your expression from "//node[1]" to "string(//node[1])".
this class can substitute the method evaluate while it is not validated. Made for Yuri Bastos and Jo?o Gilberto Magalh?es.
<?php
class XPtahQuery
{
// function returns a DOMNodeList from a relative xPath
public static function selectNodes($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
}
}
}
?>