feature symfony#5345 Adding information about empty files sent using …

…BinaryFileResponse. (kherge)

This PR was submitted for the 2.7 branch but it was merged into the 2.3 branch instead (closes symfony#5345).

Discussion
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Adding information about empty files sent using BinaryFileResponse.

Updating documentation to account for weird scenario described in symfony#5268.

Commits
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aa2ac55 Adding information about empty files sent using BinaryFileResponse.

components/http_foundation/introduction.rst

@@ -482,6 +482,20 @@ You can still set the ``Content-Type`` of the sent file, or change its ``Content
         'filename.txt'
     );
 
+.. versionadded:: 2.6
+    The ``deleteFileAfterSend()`` method was introduced in Symfony 2.6.
+
+It is possible to delete the file after the request is sent with the 
+:method:`Symfony\\Component\\HttpFoundation\\BinaryFileResponse::deleteFileAfterSend` method.
+Please note that this will not work when the ``X-Sendfile`` header is set.
+
+.. note::
+
+    If you *just* created the file during this same request, the file *may* be sent
+    without any content. This may be due to cached file stats that return zero for
+    the size of the file. To fix this issue, call ``clearstatcache(false, $file)``
+    with the path to the binary file.
+
 .. _component-http-foundation-json-response:
 
 Creating a JSON Response