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Bug
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    Resolution: Fixed
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Minor
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    3.1.6, 3.2.0-dev
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    None
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    PHP 5.6, MySQL 5.6, Firefox 44
 
set_modified_headers() checks for non-existent 'Modified-Since' request header instead of 'If-Modified-Since'.
How to reproduce: open any page containing avatars or attached images. Refresh it several times. Images are always reloaded with 200/201 status while 304 is expected.
Possible fix:
					--- includes/functions_download.php
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					+++ includes/functions_download.php
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					@@ -410,11 +410,11 @@
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					 function set_modified_headers($stamp, $browser)
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					 {
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					 	global $request;
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					 	// let's see if we have to send the file at all
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					-	$last_load 	=  $request->header('Modified-Since') ? strtotime(trim($request->header('Modified-Since'))) : false;
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					+	$last_load 	=  $request->header('If-Modified-Since') ? strtotime(trim($request->header('If-Modified-Since'))) : false;
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					 	if (strpos(strtolower($browser), 'msie 6.0') === false && !phpbb_is_greater_ie_version($browser, 7))
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					 	{
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					 		if ($last_load !== false && $last_load >= $stamp)
			 | 
		
					 		{
			 | 
		
					
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