PHP DOMXPath Register PHP functions as XPath functions

说明

public DOMXPath::registerPhpFunctions ([ mixed $restrict ] ) : void

This method enables the ability to use PHP functions within XPath expressions.

参数

restrict

Use this parameter to only allow certain functions to be called from XPath.

This parameter can be either a string (a function name) or an array of function names.

返回值

没有返回值。

范例

The following examples use book.xml which contains the following:

Example #1 book.xml

<?xml version="1.0" encoding="UTF-8"?>
<books>
 <book>
  <title>PHP Basics</title>
  <author>Jim Smith</author>
  <author>Jane Smith</author>
 </book>
 <book>
  <title>PHP Secrets</title>
  <author>Jenny Smythe</author>
 </book>
 <book>
  <title>XML basics</title>
  <author>Joe Black</author>
 </book>
</books>

Example #2 DOMXPath::registerPHPFunctions() with php:functionString

 <?php
$doc = new DOMDocument;
$doc->load('book.xml');

$xpath = new DOMXPath($doc);

// Register the php: namespace (required)
$xpath->registerNamespace("php", "http://php.net/xpath");

// Register PHP functions (no restrictions)
$xpath->registerPHPFunctions();

// Call substr function on the book title
$nodes = $xpath->query('//book[php:functionString("substr", title, 0, 3) = "PHP"]');

echo "Found {$nodes->length} books starting with 'PHP':\n";
foreach ($nodes as $node) {
    $title  = $node->getElementsByTagName("title")->item(0)->nodeValue;
    $author = $node->getElementsByTagName("author")->item(0)->nodeValue;
    echo "$title by $author\n";
}

?>

以上例程的输出类似于：

Found 2 books starting with 'PHP':
PHP Basics by Jim Smith
PHP Secrets by Jenny Smythe

Example #3 DOMXPath::registerPHPFunctions() with php:function

 <?php
$doc = new DOMDocument;
$doc->load('book.xml');

$xpath = new DOMXPath($doc);

// Register the php: namespace (required)
$xpath->registerNamespace("php", "http://php.net/xpath");

// Register PHP functions (has_multiple only)
$xpath->registerPHPFunctions("has_multiple");
 
function has_multiple($nodes) {
    // Return true if more than one author
    return count($nodes) > 1;
}
// Filter books with multiple authors
$books = $xpath->query('//book[php:function("has_multiple", author)]');

echo "Books with multiple authors:\n";
foreach ($books as $book) {
    echo $book->getElementsByTagName("title")->item(0)->nodeValue . "\n";
}

?>

以上例程的输出类似于：

Books with multiple authors:
PHP Basics

参见

DOMXPath::registerNamespace() - Registers the namespace with the DOMXPath object
DOMXPath::query() - Evaluates the given XPath expression
DOMXPath::evaluate() - Evaluates the given XPath expression and returns a typed result if possible