Optionally use symfony/var-dumper to pretty print var-dumping

Closes #308

composer.json

@@ -17,6 +17,9 @@
     "require-dev": {
         "mockery/mockery": "0.9.*"
     },
+    "suggest": {
+        "symfony/var-dumper": "^2.6"
+    },
     "autoload": {
         "psr-4": {
             "Whoops\\": "src/Whoops/"

src/Whoops/Resources/css/whoops.base.css

@@ -458,3 +458,8 @@ kbd {
   margin-right: -5px;
   border-bottom-color: rgba(0, 0, 0, 0.8)
 }
+
+pre.sf-dump {
+    padding: 0px !important;
+    margin: 0px !important;
+}

src/Whoops/Resources/views/env_details.html.php

@@ -17,7 +17,7 @@
             <?php foreach ($data as $k => $value): ?>
               <tr>
                 <td><?php echo $tpl->escape($k) ?></td>
-                <td><?php echo $tpl->escape(print_r($value, true)) ?></td>
+                <td><?php echo $tpl->escape($tpl->dump($value)) ?></td>
               </tr>
             <?php endforeach ?>
             </table>

src/Whoops/Util/TemplateHelper.php

@@ -6,6 +6,10 @@
 
 namespace Whoops\Util;
 
+use Symfony\Component\VarDumper\Cloner\VarCloner;
+use Symfony\Component\VarDumper\Dumper\CliDumper;
+use Symfony\Component\VarDumper\Dumper\HtmlDumper;
+
 /**
  * Exposes useful tools for working with/in templates
  */
@@ -58,6 +62,44 @@ class TemplateHelper
         );
     }
 
+    /**
+     * Format the given value into a human readable string.
+     *
+     * @param  mixed $value
+     * @return string
+     */
+    public function dump($value)
+    {
+        if (class_exists('Symfony\Component\VarDumper\Cloner\VarCloner')) {
+            static $dumper = null;
+
+            // re-use the same var-dumper instance, so it won't re-render the global styles/scripts on each dump.
+            if (!$dumper) {
+                $dumper = new HtmlDumper();
+
+                $styles = array(
+                    'default' => '',
+                    'num' => '',
+                    'const' => '',
+                    'str' => '',
+                    'note' => '',
+                    'ref' => '',
+                    'public' => '',
+                    'protected' => '',
+                    'private' => '',
+                    'meta' => '',
+                    'key' => '',
+                    'index' => '',
+                );
+                $dumper->setStyles($styles);
+            }
+
+            $cloner = new VarCloner();
+            return $dumper->dump($cloner->cloneVar($value));
+        }
+        return print_r($value, true);
+    }
+
     /**
      * Convert a string to a slug version of itself
      *