diff --git a/ChangeLog b/ChangeLog
index 2440c21aa4..b70ca92e14 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,7 @@ phpMyAdmin - ChangeLog
 ======================
 
 4.2.4.0 (not yet released)
+- bug #4449 Mediawiki export does not produce table header row; also fix related PHP warnings
 
 4.2.3.0 (2014-06-08)
 - bug #4423 Moving fields not working
diff --git a/export.php b/export.php
index eb30ce2d6c..c2fb468243 100644
--- a/export.php
+++ b/export.php
@@ -64,6 +64,7 @@ if (!defined('TESTSUITE')) {
             'htmlword_structure_or_data',
             'htmlword_null',
             'htmlword_columns',
+            'mediawiki_headers',
             'mediawiki_structure_or_data',
             'mediawiki_caption',
             'pdf_report_title',
diff --git a/libraries/plugins/export/ExportMediawiki.class.php b/libraries/plugins/export/ExportMediawiki.class.php
index 200ad98e55..e481ef0a3c 100644
--- a/libraries/plugins/export/ExportMediawiki.class.php
+++ b/libraries/plugins/export/ExportMediawiki.class.php
@@ -200,6 +200,7 @@ class ExportMediawiki extends ExportPlugin
         $do_mime = false,
         $dates = false
     ) {
+        $output = '';
         switch($export_mode) {
         case 'create_table':
             $columns = $GLOBALS['dbi']->getColumns($db, $table);
@@ -217,12 +218,12 @@ class ExportMediawiki extends ExportPlugin
                      . $this->_exportCRLF();
 
             // Add the table name
-            if ($GLOBALS['mediawiki_caption']) {
+            if (isset($GLOBALS['mediawiki_caption'])) {
                 $output .= "|+'''" . $table . "'''" . $this->_exportCRLF();
             }
 
             // Add the table headers
-            if ($GLOBALS['mediawiki_headers']) {
+            if (isset($GLOBALS['mediawiki_headers'])) {
                 $output .= "|- style=\"background:#ffdead;\"" . $this->_exportCRLF();
                 $output .= "! style=\"background:#ffffff\" | "
                     . $this->_exportCRLF();
@@ -293,12 +294,12 @@ class ExportMediawiki extends ExportPlugin
             . $this->_exportCRLF();
 
         // Add the table name
-        if ($GLOBALS['mediawiki_caption']) {
+        if (isset($GLOBALS['mediawiki_caption'])) {
             $output .= "|+'''" . $table . "'''" . $this->_exportCRLF();
         }
 
         // Add the table headers
-        if ($GLOBALS['mediawiki_headers']) {
+        if (isset($GLOBALS['mediawiki_headers'])) {
             // Get column names
             $column_names = $GLOBALS['dbi']->getColumnNames($db, $table);