minor #12372 [Yaml] don't override internal PHP constants (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

[Yaml] don't override internal PHP constants

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11783
| License       | MIT
| Doc PR        |

Commits
-------

376cc03 don't override internal PHP constants

Author: fabpot

Fragment/HIncludeFragmentRenderer.php

@@ -11,10 +11,6 @@
 
 namespace Symfony\Component\HttpKernel\Fragment;
 
-if (!defined('ENT_SUBSTITUTE')) {
-    define('ENT_SUBSTITUTE', 8);
-}
-
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\Templating\EngineInterface;
@@ -111,11 +107,16 @@ public function render($uri, Request $request, array $options = array())
         }
         $renderedAttributes = '';
         if (count($attributes) > 0) {
+            if (version_compare(PHP_VERSION, '5.4.0', '>=')) {
+                $flags = ENT_QUOTES | ENT_SUBSTITUTE;
+            } else {
+                $flags = ENT_QUOTES;
+            }
             foreach ($attributes as $attribute => $value) {
                 $renderedAttributes .= sprintf(
                     ' %s="%s"',
-                    htmlspecialchars($attribute, ENT_QUOTES | ENT_SUBSTITUTE, $this->charset, false),
-                    htmlspecialchars($value, ENT_QUOTES | ENT_SUBSTITUTE, $this->charset, false)
+                    htmlspecialchars($attribute, $flags, $this->charset, false),
+                    htmlspecialchars($value, $flags, $this->charset, false)
                 );
             }
         }