[wp-trac] [WordPress Trac] #37889: "Add post" overwriting a previous post in 4.6

[WordPress Trac]

#37889: "Add post" overwriting a previous post in 4.6
-------------------------------+-----------------------------
 Reporter:  tgelles            |       Owner:
     Type:  defect (bug)       |      Status:  closed
 Priority:  normal             |   Milestone:
Component:  Posts, Post Types  |     Version:
 Severity:  normal             |  Resolution:  invalid
 Keywords:                     |     Focuses:  administration
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Comment (by SergeyBiryukov):

 If you're experiencing this issue, try adding this to the active theme’s
 `functions.php` file to see if it makes a difference:
 {{{
 function add_pragma_no_cache_header( $headers ) {
         $headers['Pragma'] = 'no-cache';
         return $headers;
 }
 add_filter( 'nocache_headers', 'add_pragma_no_cache_header' );
 }}}
 `Pragma` is a client request header that normally shouldn’t be present in
 server response. In earlier WordPress versions it was added for
 compatibility with older IE versions that didn’t understand `Cache-
 Control`. In WordPress 4.6 it was removed as no longer necessary, see
 [37944].

 However, some environments might have weird or invalid cache control
 headers, and restoring `Pragma` might help in that case. I’ve seen an
 [https://habrahabr.ru/post/312696/ article on this issue] (in Russian),
 although the author didn’t fully understand the change and fights the
 symptom instead of the cause.

 In a recent [https://wordpress.org/support/topic/wordpress-is-creating-
 revisions-instead-of-new-posts/#post-9030853 support forums thread], these
 Apache settings were the culprit:
 {{{
 <IfModule expires_module>
   ExpiresActive On
   ExpiresByType text/html "access plus 600 seconds"
   ExpiresByType application/xhtml+xml "access plus 600 seconds"
 </IfModule>

 <IfModule headers_module>
   <FilesMatch "\\.(x?html?|php)$">
     Header set Cache-Control "max-age=600, private, must-revalidate"
   </FilesMatch>
   Header unset ETag
   Header unset Last-Modified
 </IfModule>
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/37889#comment:12>
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