Trouble printing array of titles and urls - php

Question

I'm not very good at PHP.
I have a folder of .html files that will change often, and then I want to search through the folder, parse the <h1> tags, and then print/echo each <h1> tag and its url.
Getting the <h1> tags out of the .html files was easy enough with some Googling, but I cannot seem to print a list of <h1> titles and their corresponding URL's.
Here is what I have so far:
$url_list = glob('posts/*.html'); // Searches for all files and folders in above directory that end in .html.
foreach ($url_list as $url) { // Creates an array of post URL's and title <h1> tags.
$post = new DOMDocument(); // Creates string to load blog post.
$post->loadHTMLFile($url); // Loads blog post into string $post from its URL.
$h1_tags = $post->getElementsByTagName('h1'); // Finds all <h1> tags.
$first_h1 = $h1_tags->item(0); // Gets value of first <h1> tag.
$title = $first_h1->nodeValue; // Sets $title to value of first <h1> tag.
if (!empty($title)) { // Will only run on files which have a date in their metadata.
$post_list[$url] = $title;
$post_list[$title] = $url;
}
}
sort($post_list); // Sorts list of posts in alphabetical order.
$num = 1;
foreach ($post_list as $title) { //
echo "<h2>".($num++).". {$title} = {$url}</h2>";
}

Answer 1

You are adding the titles and URL's into the same list - but reversed. If you build up your data as...
if (!empty($title)) { // Will only run on files which have a date in their metadata.
$post_list[$title] = $url;
}
So this only adds it in once, and then output it like...
foreach ($post_list as $title => $url) { //
echo "<h2>".($num++).". {$title} = {$url}</h2>";
}
Edit: change sort() to asort()