minor #5433 Warn users of older PHP versions Crawler might not decode…

… HTML entities properly (jakzal, javiereguiluz)

This PR was merged into the 2.3 branch.

Discussion
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Warn users of older PHP versions Crawler might not decode HTML entities properly

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.3,<2.7
| Fixed tickets | -

Commits
-------

699e637 Reworded the notice as a caution
c47ec88 [DomCrawler] Warn users of older PHP versions Crawler might not decode html entities properly.

components/dom_crawler.rst

@@ -234,6 +234,12 @@ and :phpclass:`DOMNode` objects:
 
     The ``html`` method is new in Symfony 2.3.
 
+    .. caution::
+
+        Due to an issue in PHP, the ``html()`` method returns wrongly decoded HTML
+        entities in PHP versions lower than 5.3.6 (for example, it returns ``•``
+        instead of ``•``).
+
 Links
 ~~~~~