Php/docs/domxpath.evaluate
DOMXPath::evaluate
(PHP 5 >= 5.1.0, PHP 7)
DOMXPath::evaluate — Evaluates the given XPath expression and returns a typed result if possible
说明
public DOMXPath::evaluate
( string $expression
[, DOMNode $contextnode
[, bool $registerNodeNS = true
]] ) : mixed
Executes the given XPath expression and returns
a typed result if possible.
参数
expression- The XPath expression to execute.
contextnode- The optional
contextnodecan be specified for doing relative XPath queries. By default, the queries are relative to the root element. registerNodeNS- The optional
registerNodeNScan be specified to disable automatic registration of the context node.
返回值
Returns a typed result if possible or a DOMNodeList
containing all nodes matching the given XPath expression.
If the expression is malformed or the
contextnode is invalid,
DOMXPath::evaluate() returns false.
范例
Example #1 Getting the count of all the english books
<?php$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
