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diff --git a/blog/2021-04-23-php-comment-system.org b/blog/2021-04-23-php-comment-system.org new file mode 100644 index 0000000..38132fd --- /dev/null +++ b/blog/2021-04-23-php-comment-system.org @@ -0,0 +1,262 @@ ++++ +date = 2021-04-23 +title = "Roll Your Own Static Commenting System in PHP" +description = "Learn how to skip the tedium of finding the proper commenting system by simply rolling your own in PHP." +draft = false ++++ + +## The Terrible-ness of Commenting Systems + +The current state of affairs regarding interactive comment systems is, well, +terrible. It is especially awful if you're a privacy conscious person who does +not generally load third-party scripts or frames on the websites you visit. + +Even further, many comment systems are charging exorbitant fees for something +that should be standard. + +Of course, there are some really terrible options: + +- Facebook Comments +- Discourse + +There are some options that are better but still use too many scripts, frames, +or social integrations on your web page that could impact some users: + +- Disqus +- Isso +- Remark42 + +Lastly, I looked into a few unique ways of generating blog comments, such as +using Twitter threads or GitHub issues to automatically post issues. However, +these both rely on external third-party sites that I don't currently use. + +## Stay Static with Server-Side Comments + +The main issue for my personal use-case is that my blog is completely, 100% +static. I use PHP on the back-end but website visitors only see HTML and a +single CSS file. No external javascript and no embedded frames. + +So, how do we keep a site static and still allow users to interact with blog +posts? The key actually pretty simple - I'm already using PHP, so why not rely +on the classic HTML `<form>` and a PHP script to save the comments somewhere? As +it turns out, this was a perfect solution for me. + +The second issue for my personal use-case is that I am trying to keep the +contents of my website accessible over time, as described by @brandur, in his +post entitled +[Blog with Markdown + Git, and degrade gracefully through time](https://brandur.org/fragments/graceful-degradation-time) +. + +This means I cannot rely on a database for comments, since I do not rely on a +database for any other part of my websites. + +I blog in plain Markdown files, commit all articles to Git, and ensure that +future readers will be able to see the source data long after I'm gone, or the +website has gone offline. However, I still haven't committed any images served +on my blog to Git, as I'm not entirely sold on Git LFS yet - for now, images can +be found at [img.0x4b1d.org](https://img.0x4b1d.org). + +Saving my comments back to the Git repository ensures that another aspect of my +site will degrade gracefully. + +## Create a Comment Form + +Okay, let's get started. The first step is to create an HTML form that users can +see and utilize to submit comments. This is fairly easy and can be changed +depending on your personal preferences. + +Take a look at the code block below for the form I currently use. Note that +`<current-url>` is replaced automatically in PHP with the current post's URL, so +that my PHP script used later will know which blog post the comment is related +to. + +The form contains the following structure: + +1. `<form>` - This is the form and will determine which PHP script to send the + comment to. +2. `<section hidden>` - This section is hidden from the user and is used to + ensure that we know which blog post sent the comment. +3. `<section>` Display Name (Optional) - Used to accept a display name, if + entered. +4. `<section>` Comment (Required) - Used to accept the user's full comment. + Markdown is allowed. +5. `<button>` - A button to submit the form. + +```html +<form action="/comment.php" method="POST"> + <h3>Leave a Comment</h3> + <section hidden> + <label class="form-label" for="postURL">Post URL</label> + <input + class="form-control" + id="postURL" + name="postURL" + type="text" + value="<current-url>" + /> + </section> + <section> + <label class="form-label" for="userName">Display Name</label> + <input + class="form-control" + id="userName" + name="userName" + placeholder="John Doe" + type="text" + /> + </section> + <section> + <label class="form-label" for="userContent">Your Comment</label> + <textarea + class="form-control" + id="userContent" + name="userContent" + rows="3" + placeholder="# Feel free to use Markdown" + aria-describedby="commentHelp" + required + ></textarea> + <div id="commentHelp" class="form-text"> + Comments are saved as Markdown and cannot be edited or deleted. + </div> + </section> + <button type="submit">Submit</button> +</form> +``` + +## Handle Comments via POST + +Now that we have a form and can submit comments, we need to create a PHP script +so that the server can fetch the comment data and save it. Make sure your PHP +script name matches the name you entered in the `action` field in your form. + +See the code block below for the contents of my `comment.php` script. We perform +the following tasks in this script: + +1. Grab the POST data from the HTML form. +2. Sanitize the comment data with `htmlentities`. +3. Set the display name to `Anonymous` if it was left blank. +4. Create a PHP object that combines all of this data. +5. Check if our destination file `comments.json` exists. +6. If so, convert the PHP object to JSON and save it to the file. +7. If the `comments.json` file does not exist, the script will exit with an + error. You can alter this to ensure it creates the script, but my source code + includes the file by default, so it will always exist. +8. Finally, send the user back to the `#comments` section of the blog post they + just read. + +```php +// Get the content sent from the comment form +$comment = htmlentities($_POST['userContent']); +$post_url = $_POST['postURL']; + +// Set default values if blank +if (isset($_POST['userName']) && trim($_POST['userName']) !== "") { + $username = $_POST['userName']; +} else { + $username = 'Anonymous'; +} + +// Create an empty PHP object +$user_object = new stdClass(); + +// Add object content +$user_object->timestamp = date('Y-m-d H:i:s'); +$user_object->username = $username; +$user_object->comment = $comment; +$user_object->post_url = $post_url; + +// Append JSON to file +$file_name = 'comments.json'; +if (file_exists($file_name)) { + $source_data = file_get_contents($file_name); + $temp_array = json_decode($source_data); + array_push($temp_array, $user_object); + $json_data = json_encode($temp_array, JSON_PRETTY_PRINT); + file_put_contents($file_name, $json_data); +} else { + die('Error: The "comments.json" file does not exist.'); +} + +// Send the user back +header('Location: ' . $post_url . '#comments'); +``` + +If you're using Apache, make sure the `www-data` user on your server has the +correct permissions to your website directory or else it will not be able to +write to `comments.json`. + +```sh +chgrp -R www-data /path/to/website/ +chmod -R g+w comments.json +``` + +## Display User Comments + +Now that we can submit comments, and they are saved to the `comments.json` file, +let's make sure we can show those comments in each blog post. + +The code block below shows the function I use to decode my `comments.json` file, +check if the comments apply to the current post, and then display them. + +This piece of code should **really** be inside a function (or at least in an +organized PHP workflow). Don't just copy-and-paste and expect it to work. You +need to at least supply a `$query` variable depending on the page visited. + +```php +$query = 'your-blog-post.html'; + +// Load saved comments +$comments_file = 'comments.json'; +$comments_raw = file_get_contents($comments_file); +$comments = json_decode($comments_raw); +$comment_section = '<section id="comments" class="comments"><h3>Comments</h3>'; +foreach ($comments as $comment) { + if ($comment->post_url == "https://example.com/post/" . $query) { + // Assign metadata to variables + $comment_timestamp = $comment->timestamp; + $comment_username = $comment->username; + $comment_content = $comment->comment; + + // Parse the comment, in case it contains Markdown + $comment_md = Parsedown::instance()->text($comment_content); + $comment_html = new DOMDocument(); + $comment_html->loadHTML($comment_md); + $comment_html_links = $comment_html->getElementsByTagName('a'); + foreach ($comment_html_links as $comment_html_link) { + $comment_html_link->setAttribute('rel', 'noreferrer'); + $comment_html_link->setAttribute('target', '_blank'); + } + $comment_secured_html = $comment_html->saveHTML(); + + // Apply metadata to comments section + $comment_section .= '<div class="user-comment"><div class="row"><label>Timestamp:</label><p>' . $comment_timestamp . '</p></div><div class="row"><label>Name:</label><p>' . $comment_username . '</p></div><div class="row markdown"><label>Comment:</label><div class="comment-markdown">' . $comment_secured_html . '</div></div></div>'; + } +} + +echo $comment_section; +``` + +## Bonus: Create a 'Recent Comments' Page + +Finally, the last part of my current system is to create a Recent Comments page +so that I can easily check-in on my blog and moderate any spam. As an +alternative, you could use PHP's `mail()` function to email you for each blog +comment. + +The code to do this is literally the same code as the previous section, I just +make sure it is printed when someone visits `https://example.com/comments/`. + +## Possible Enhancements + +This comment system is by no means a fully-developed system. I have noted a few +possible enhancements here that I may implement in the future: + +- Create a secure moderator page with user authentication at + `https://blog.example.com/mod/`. This page could have the option to edit or + delete any comment found in `comments.json`. +- Create a temporary file, such as `pending_comments.json`, that will store + newly-submitted comments and won't display on blog posts until approved by a + moderator. +- Create a `/modlog/` page with a chronological log, showing which moderator + approved which comments and why certain comments were rejected. |