DOMXPath::evaluate
Evaluates the given XPath expression and returns a typed result if possible
Description
public mixed DOMXPath::evaluate(string $expression, DOMNodenull $contextNode = null, bool $registerNodeNS = true)
Parameters
-
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
-
Whether to automatically register the in-scope namespace prefixes of the context node to the DOMXPath object.
This can be used to avoid needing to call DOMXPath::registerNamespace manually for each in-scope namespaces.
When a namespace prefix conflict exists, only the nearest descendant namespace prefix is registered.
Errors/Exceptions
The following errors are possible when using an expression that invokes
PHP callbacks.
-
Throws an Error if
a PHP callback is invoked but there were no callbacks registered,
or if the named callback was not registered.
-
Throws a TypeError if
the
php:function syntax is used and the handler
name is not a string.
-
Throws an Error if
a non-DOM object was returned from a callback.
Return Values
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.
Examples
Example #1 Getting the count of all the english books
<?php
$doc = new DOMDocument;
$doc->load('examples/book-dcobook.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";
?>
The above example will output:
There are 2 english books