+/** Include required files from SM */
+include_once(SM_PATH . 'functions/imap_mailbox.php');
+
+/**
+ * Output a SquirrelMail page header, from <!doctype> to </head>
+ * Always set up the language before calling these functions.
+ *
+ * Since 1.5.1 function sends http headers. Function should be called
+ * before any output is started.
+ * @param string title the page title, default SquirrelMail.
+ * @param string xtra extra HTML to insert into the header
+ * @param bool do_hook whether to execute hooks, default true
+ * @param bool frames generate html frameset doctype (since 1.5.1)
+ * @param bool $browser_cache_ok When TRUE, it's OK to leave out the
+ * no-cache browser headers (OPTIONAL;
+ * default = FALSE, send no-cache headers)
+ * @return void
+ */
+function displayHtmlHeader( $title = 'SquirrelMail', $xtra = '', $do_hook = TRUE, $frames = FALSE, $browser_cache_ok=FALSE ) {
+ global $squirrelmail_language, $sTemplateID, $oErrorHandler, $oTemplate;
+
+ if ( !sqgetGlobalVar('base_uri', $base_uri, SQ_SESSION) ) {
+ global $base_uri;
+ }
+ global $custom_css, $pageheader_sent, $theme, $theme_default, $text_direction,
+ $default_fontset, $chosen_fontset, $default_fontsize, $chosen_fontsize,
+ $chosen_theme, $chosen_theme_path, $user_themes, $user_theme_default;
+
+ // add no cache headers here
+ //
+ if (!$browser_cache_ok) {
+//FIXME: should change all header() calls in SM core to use $oTemplate->header()!!
+ $oTemplate->header('Pragma: no-cache'); // http 1.0 (rfc1945)
+ $oTemplate->header('Cache-Control: private, no-cache, no-store, must-revalidate, max-age=0'); // http 1.1 (rfc2616)
+ $oTemplate->header('Expires: Sat, 1 Jan 2000 00:00:00 GMT');
+//TODO: is this needed? $oTemplate->header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . 'GMT');
+ }
+ /* prevent information leakage about read emails by forbidding Firefox
+ * to do preemptive DNS requests for any links in the message body. */
+ $oTemplate->header('X-DNS-Prefetch-Control: off');