implemented following users to receive (opt-in) email notifications when they publish an article.

functions/functions.php

@@ -1,17 +1,36 @@
 <?php
+include_once 'functions/init.php';
 
-if (!empty($_FILES['upload'])) {
-    require_once '../vendor/autoload.php';
+use Postmark\PostmarkClient;
 
-    // Load environment variables.
-    $dotenv = Dotenv\Dotenv::createImmutable(__DIR__ . '/../');
-    $dotenv->safeLoad();
+if (!empty($_FILES['upload']))
     upload($_FILES['upload'], $_ENV['UPLOAD_TMP_FQ_PATH'], isset($_POST['filename']) ? $_POST['filename'] : null);
+
+function notify_users($emails, $auther_username, $article_id, $article_title, $excerpt)
+{
+    foreach ($emails as $email) {
+        $email_html = '
+            <h1>' . $article_title . '</h1>
+            <p>An author you follow just published a new article! Read it <a href="https://vintagecoding.net/articles.php?view=read&article_id=' . $article_id . '" target="_blank">here</a></p>
+            <p><strong>Here is a snippet from the article!</strong></p>
+            <p>' . $excerpt . '</p>
+        ';
+
+        $client = new PostmarkClient($_ENV['POSTMARK_API_TOKEN']);
+
+        $client->sendEmail(
+            'mailer@joshashton.dev',
+            $email,
+            $auther_username . ' just published a new article! - vintagecoding.net',
+            $email_html
+        );
+    }
 }
 
 function delete_dir($dir)
 {
-    if (!is_dir($dir)) return false;
+    if (!is_dir($dir))
+        return false;
 
     if (substr($dir, strlen($dir) - 1, 1) != '/') {
         $dir .= '/';
@@ -28,7 +47,8 @@ function delete_dir($dir)
 
 function delete_file($file)
 {
-    if (!file_exists($file)) return false;
+    if (!file_exists($file))
+        return false;
 
     unlink($file);
 }
@@ -54,7 +74,7 @@ function upload($input, $dest_dir, $filename = null)
 
             break;
         default:
-            # code...
+            // code...
             break;
     }
 
@@ -66,7 +86,7 @@ function upload($input, $dest_dir, $filename = null)
 
 function crop_image($img_path, $x, $y, $height, $width)
 {
-    //$dest = $_ENV['UPLOAD_TMP_FQ_PATH'];
+    // $dest = $_ENV['UPLOAD_TMP_FQ_PATH'];
     $dest = '/tmp/';
     // Get the image type
     $imageType = exif_imagetype($img_path);
@@ -80,11 +100,11 @@ function crop_image($img_path, $x, $y, $height, $width)
             $sourceImage = imagecreatefrompng($img_path);
             break;
         default:
-            return false; // Unsupported image type
+            return false;  // Unsupported image type
     }
 
     if (!$sourceImage)
-        return false; // Failed to create image resource
+        return false;  // Failed to create image resource
 
     // Create a new image resource for the cropped image
     $croppedImage = imagecreatetruecolor($width, $height);
@@ -109,7 +129,7 @@ function crop_image($img_path, $x, $y, $height, $width)
     imagedestroy($sourceImage);
     imagedestroy($croppedImage);
 
-    return true; // Cropping successful
+    return true;  // Cropping successful
 }
 
 /*
@@ -132,7 +152,7 @@ function extract_content_from_tag($string, $start, $end)
 {
     $ini = strpos($string, $start);
     if ($ini != 0)
-        return "nope";
+        return 'nope';
 
     $ini += strlen($start);
     $len = strpos($string, $end, $ini) - $ini;
@@ -151,9 +171,7 @@ function check_csv_upload($target)
 
 function pretty_dump($arr)
 {
-    echo '
-    <pre>
-        ' . print_r($arr) . '
-    </pre>
-    ';
+    echo '<pre>';
+    print_r($arr);
+    echo '</pre>';
 }