Add login error message

src/classes/page.php

@@ -215,4 +215,62 @@ class Page
         </html>
         <?php
     }
+
+    public function message(string $content = '', string $header = '', string $type = ''): void
+    {
+        $containerClasses = array('ui', 'message');
+        $iconClasses      = array('ui', 'icon');
+
+        switch ($type) {
+            case 'error':
+                $containerClasses[] = 'error icon';
+                $iconClasses[] = 'exclamation triangle';
+                break;
+
+            case 'warning':
+                $containerClasses[] = 'warning';
+                $iconClasses[] = 'exclamation circle';
+                break;
+
+            case 'info':
+                $containerClasses[] = 'info';
+                $iconClasses[] = 'info circle';
+                break;
+        }
+
+        $containerClass = implode(' ', $containerClasses);
+        $iconClass      = implode(' ', $iconClasses);
+        ?>
+        <div class="<?= $containerClass ?>">
+            <?php if ($type) { ?>
+                <i class="<?= $iconClass ?>"></i>
+            <?php } ?>
+
+            <div class="content">
+                <?php if ($header) { ?>
+                    <div class="header"><?= $header ?></div>
+                <?php } ?>
+
+                <?php if ($content) { ?>
+                    <p><?= $content ?></p>
+                <?php } ?>
+            </div>
+        </div>
+        <?php
+    }
+
+    public function error(string $content, string $header = ''): void
+    {
+        $this->message($content, $header, 'error');
+    }
+
+    public function warning(string $content, string $header = ''): void
+    {
+        $this->message($content, $header, 'warning');
+    }
+
+    public function info(string $content, string $header = ''): void
+    {
+        $this->message($content, $header, 'info');
+    }
 }

src/pages/login.php

@@ -1,7 +1,7 @@
 <?php
 
 /**
- * login.php
+ * The user login page.
  *
  * @author Jay Trees <github.jay@grandel.anonaddy.me>
  */
@@ -25,9 +25,9 @@ if (isset($_POST['email'], $_POST['password'])) {
          AND `password` = "' . $password . '";'
     )->fetch();
 
-    if (false === $user) {
+    $success = false !== $user;
-        # code...
+
-    } else {
+    if ($success) {
         $_SESSION['user'] = $user;
     }
 }
@@ -44,6 +44,12 @@ $page->navigation();
     <div class="ui container">
         <h1 class="ui header"><?= $page->title ?></h1>
 
+        <?php
+        if (!$success) {
+            $page->error('Invalid credentials!', 'Error');
+        }
+        ?>
+
         <div class="ui segment">
             <form class="ui form" method="post">
                 <div class="field">