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
$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.
更新日志
| 版本 | 说明 |
|---|---|
| 5.3.3 |
The registerNodeNS parameter was added.
|
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