Check some requirements before installation

framework/core/src/Install/Actions/IndexAction.php

@@ -40,8 +40,29 @@ class IndexAction extends HtmlAction
 
         $view->logo = $this->view->make('flarum.install::logo');
 
+        $errors = [];
+
+        if (version_compare(PHP_VERSION, '5.5.0', '<')) {
+            $errors[] = [
+                'message' => '<strong>PHP 5.5+</strong> is required.',
+                'detail' => 'You are running version '.PHP_VERSION.'.'
+            ];
+        }
+
+        foreach (['mbstring', 'pdo_mysql'] as $extension) {
+            if (! extension_loaded($extension)) {
+                $errors[] = [
+                    'message' => 'The <strong>'.$extension.'</strong> extension is required.'
+                ];
+            }
+        }
+
+        if (count($errors)) {
+            $view->content = $this->view->make('flarum.install::errors');
+            $view->content->errors = $errors;
+        } else {
             $view->content = $this->view->make('flarum.install::install');
-        $view->content->input = [];
+        }
 
         return $view;
     }

framework/core/views/install/app.blade.php

@@ -128,6 +128,34 @@
         -webkit-animation-name: fadeIn;
         animation-name: fadeIn;
       }
+
+      .Errors {
+        margin-top: 50px;
+      }
+      .Errors .Error:first-child {
+        border-top-left-radius: 4px;
+        border-top-right-radius: 4px;
+      }
+      .Errors .Error:last-child {
+        border-bottom-left-radius: 4px;
+        border-bottom-right-radius: 4px;
+      }
+      .Error {
+        background: #EDF2F7;
+        margin: 0 0 1px;
+        padding: 20px 25px;
+        text-align: left;
+      }
+      .Error-message {
+        font-size: 16px;
+        color: #3C5675;
+        font-weight: normal;
+        margin: 0;
+      }
+      .Error-detail {
+        font-size: 13px;
+        margin: 5px 0 0;
+      }
     </style>
   </head>
 

framework/core/views/install/errors.blade.php

@@ -1,12 +1,14 @@
 <h2>Hold Up!</h2>
 
-<p>These errors must be resolved before you can continue the installation.</p>
+<p>These errors must be resolved before you can continue the installation. If you're having trouble, get help on the <a href="http://flarum.org/docs/troubleshooting" target="_blank">Flarum website</a>.</p>
 
 <div class="Errors">
   @foreach ($errors as $error)
     <div class="Error">
-      <h3 class="Error-message">{{ $error['message'] }}</h3>
+      <h3 class="Error-message">{!! $error['message'] !!}</h3>
-      <p class="Error-detail">{{ $error['detail'] }}</p>
+      @if (! empty($error['detail']))
+        <p class="Error-detail">{!! $error['detail'] !!}</p>
+      @endif
     </div>
   @endforeach
 </div>