php|architect's Guide to Web Scraping with PHP - Wind Business ...

104 ” DOM Extension
// A slightly more specific way (better if there are multiple lists)
if ($list = $doc->getElementById(’thelist’)) {
$listItems = $list->getElementsByTagName(’li’);
}
// Yet another way if the list doesn’t have an id
$lists = $doc->getElementsByTagName(’ul’);
if ($lists->length) {
$list = $lists->item(0);
$listItems = $list->getElementsByTagName(’li’);
}
// Outputs "thelist" (without quotes)
echo $list->getAttribute(’id’);
// Outputs "Foo" on one line, then "Bar" on another
foreach ($listItems as $listItem) {
echo $listItem->nodeValue, PHP_EOL;
}
// Outputs text content inside and
echo $list->nodeValue;
?>
XPath and DOMXPath
Somewhat similar to the way that regular expressions allow instances of character
patterns to be found within strings, XPath allows instances of node patterns to be
found within XML-compatible documents. Both technologies accomplish their purpose
by providing a syntax comprised of meta-characters to express these patterns
in a concise and succinct way. With the DOM extension, support for version 1.0 of
the XPath standard is implemented as the DOMXPath class.
The DOMXPath constructor has a single required parameter: an existing DOMDocument
instance on which queries will be performed. DOMXPath has two other relevant methods:
evaluate and query. Both accept a string containing an XPath expression with
which to query the document as their first parameter.
Optionally, a DOMNode instance associated with the document may be passed in as
the second parameter ($contextNode) for either method. When specified, that node