Use Debugger to output constant values.

As of PHP 5.6 constants can contain non-scalar data.
Debugger::exportVar() handles all sorts of data more gracefully.

Refs #401

Author: markstory

src/Template/Element/environment_panel.ctp

@@ -14,6 +14,7 @@
  * @link          http://cakephp.org CakePHP(tm) Project
  * @license       http://www.opensource.org/licenses/mit-license.php MIT License
  */
+use Cake\Error\Debugger;
 use Cake\Utility\Inflector;
 ?>
 
@@ -31,7 +32,7 @@ use Cake\Utility\Inflector;
         <?php foreach ($app as $key => $val): ?>
         <tr>
             <td><?= h($key) ?></td>
-            <td><?= h($val) ?></td>
+            <td><?= h(Debugger::exportVar($val)) ?></td>
         </tr>
         <?php endforeach; ?>
     </tbody>
@@ -56,7 +57,7 @@ use Cake\Utility\Inflector;
         <?php foreach ($cake as $key => $val): ?>
         <tr>
             <td><?= h($key) ?></td>
-            <td><?= h($val) ?></td>
+            <td><?= h(Debugger::exportVar($val)) ?></td>
         </tr>
         <?php endforeach; ?>
     </tbody>
@@ -107,7 +108,7 @@ use Cake\Utility\Inflector;
             <?php foreach ($hidef as $key => $val): ?>
             <tr>
                 <td><?= h($key) ?></td>
-                <td><?= h($val) ?></td>
+                <td><?= h(Debugger::exportVar($val)) ?></td>
             </tr>
             <?php endforeach; ?>
         </tbody>