Regex with DOMDocument in PHP

user_1231450 0
Viewed 534

Consider the following PHP snippet:

<?php

$html = <<<DATA
<p>Lorem Ipsum is simply dummy text</p> <p>Lorem Ipsum is <a href="http://www.google.com">simply</a> dummy text</p><a href="http://www.youtube.com/watch?v=DUQi_R4SgWo" target="_blank" rel="noopener">Check out the video here!</a>. <p>Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged.</p> <a href="http://www.youtube.com/watch?v=A_6gNZCkajU" target="_blank" rel="noopener">Video here</a> <p>It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.</p>
DATA;

# set up the DOM
$dom = new DOMDocument();
$dom->loadHTML($html, LIBXML_HTML_NODEFDTD | LIBXML_HTML_NOIMPLIED);

# set up the xpath
$xpath = new DOMXPath($dom);

# set up the regex
$regex = '~\?v=([^&]+)~';

foreach ($xpath->query("a[contains(@href, 'youtube')]/@href") as $link) {
    preg_match($regex, $link->nodeValue, $matches);
    if ($matches) {
        $id = $matches[1];
        echo "$id\n";
    }
}
?>

This sets up the DOM on an HTML string and gets the YouTube links with the help of an xpath query and a regular expression afterwards.
The snippet yields

DUQi_R4SgWo
A_6gNZCkajU

Now, I'd like to replace the foreach loop with:

$regex = '~\?v=([^&]+)~';

$xpath->registerPHPFunctions();
$xpath->registerNamespace("php", "http://php.net/xpath");
$links = $xpath->query("a[php:functionString('preg_match', '$regex', href, '$matches')]/@href");

This finds the same links but does not save anything into $matches - why?

domdocument php regex
2 Answers

Quick scan of the underlying engine code: it does not support pass-by-reference.

To get around that, use your own wrapper:

$xpath->registerNamespace('php', 'http://php.net/xpath');
$xpath->registerPHPFunctions('match');
$links = $xpath->query("a[php:functionString('match', @href)]/@href");

function match($href) {
    $regex = '~\?v=([^&]+)~';
    $rc = preg_match($regex, $href, $matches);
    var_dump($matches[1]); // store this somewhere
    return $rc;
}

See it live on 3v4l.org.

user_29087240 
$matches = array();
function mymatch($string){
  $regex = '~\?v=([^&]+)~';
  global $matches;
  preg_match_all($regex, $string, $matches);

}
$xpath->registerPHPFunctions('mymatch');
$xpath->registerNamespace("php", "http://php.net/xpath");
$links = $xpath->query("a[php:functionString('mymatch',@href)]/@href");
print_r($matches);
user_35992370
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