Using PHP to get DOM Element - php

Question

I'm struggling big time understanding how to use the DOMElement object in PHP. I found this code, but I'm not really sure it's applicable to me:
$dom = new DOMDocument();
$dom->loadHTML("index.php");
$div = $dom->getElementsByTagName('div');
foreach ($div->attributes as $attr) {
$name = $attr->nodeName;
$value = $attr->nodeValue;
echo "Attribute '$name' :: '$value'<br />";
}
Basically what I need is to search the DOM for an element with a particular id, after which point I need to extract a non-standard attribute (i.e. one that I made up and put on with JS) so I can see the value of that. The reason is I need one piece from the $_GET and one piece that is in the HTML based from a redirect. If someone could just explain how I use DOMDocument for this purpose, that would be helpful. I'm really struggling understanding what's going on and how to properly implement it, because I clearly am not doing it right.
EDIT (Where I'm at based on comment):
This is my code lines 4-26 for reference:
<div id="column_profile">
<?php
require_once($_SERVER["DOCUMENT_ROOT"] . "/peripheral/profile.php");
$searchResults = isset($_GET["s"]) ? performSearch($_GET["s"]) : "";
$dom = new DOMDocument();
$dom->load("index.php");
$divs = $dom->getElementsByTagName('div');
foreach ($divs as $div) {
foreach ($div->attributes as $attr) {
$name = $attr->nodeName;
$value = $attr->nodeValue;
echo "Attribute '$name' :: '$value'<br />";
}
}
$div = $dom->getElementById('currentLocation');
$attr = $div->getAttribute('srckey');
echo "<h1>{$attr}</a>";
?>
</div>
<div id="column_main">
Here is the error message I'm getting:
Warning: DOMDocument::load() [domdocument.load]: Extra content at the end of the document in ../public_html/index.php, line: 26 in ../public_html/index.php on line 10
Fatal error: Call to a member function getAttribute() on a non-object in ../public_html/index.php on line 21

Answer 1

getElementsByTagName returns you a list of elements, so first you need to loop through the elements, then through their attributes.
$divs = $dom->getElementsByTagName('div');
foreach ($divs as $div) {
foreach ($div->attributes as $attr) {
$name = $attr->nodeName;
$value = $attr->nodeValue;
echo "Attribute '$name' :: '$value'<br />";
}
}
In your case, you said you needed a specific ID. Those are supposed to be unique, so to do that, you can use (note getElementById might not work unless you call $dom->validate() first):
$div = $dom->getElementById('divID');
Then to get your attribute:
$attr = $div->getAttribute('customAttr');
EDIT: $dom->loadHTML just reads the contents of the file, it doesn't execute them. index.php won't be ran this way. You might have to do something like:
$dom->loadHTML(file_get_contents('http://localhost/index.php'))

Answer 2

You won't have access to the HTML if the redirect is from an external server. Let me put it this way: the DOM does not exist at the point you are trying to parse it. What you can do is pass the text to a DOM parser and then manipulate the elements that way. Or the better way would be to add it as another GET variable.
EDIT: Are you also aware that the client can change the HTML and have it pass whatever they want? (Using a tool like Firebug)