diff --git a/import.php b/import.php
index e68ab3206..89f8a292f 100644
--- a/import.php
+++ b/import.php
@@ -76,17 +76,17 @@ if ($import_type == 'table') {
     $goto = 'server_import.php';
 } else {
     if (empty($goto) || !preg_match('@^(server|db|tbl)(_[a-z]*)*\.php$@i', $goto)) {
-        if (isset($table) && isset($db)) {
+        if (strlen($table) && strlen($db)) {
             $goto = 'tbl_structure.php';
-        } elseif (isset($db)) {
+        } elseif (strlen($db)) {
             $goto = 'db_structure.php';
         } else {
             $goto = 'server_sql.php';
         }
     }
-    if (isset($table) && isset($db)) {
+    if (strlen($table) && strlen($db)) {
         $common = PMA_generate_common_url($db, $table);
-    } elseif (isset($db)) {
+    } elseif (strlen($db)) {
         $common = PMA_generate_common_url($db);
     } else {
         $common = PMA_generate_common_url();
@@ -97,7 +97,7 @@ if ($import_type == 'table') {
 }
 
 
-if (isset($db)) {
+if (strlen($db)) {
     PMA_DBI_select_db($db);
 }
 
diff --git a/libraries/mysql_charsets.lib.php b/libraries/mysql_charsets.lib.php
index 510246fd7..f5896a2e5 100644
--- a/libraries/mysql_charsets.lib.php
+++ b/libraries/mysql_charsets.lib.php
@@ -130,7 +130,7 @@ if (PMA_MYSQL_INT_VERSION >= 40100){
             // the query does not work if this string is in double quotes
             // and MySQL is running in ANSI mode
             $return = PMA_DBI_fetch_value('SHOW VARIABLES LIKE \'collation_database\'', 0, 1);
-            if (isset($GLOBALS['db']) && $db !== $GLOBALS['db']) {
+            if ($db !== $GLOBALS['db']) {
                 PMA_DBI_select_db($GLOBALS['db']);
             }
             return $return;
diff --git a/libraries/navigation_header.inc.php b/libraries/navigation_header.inc.php
index 360c489bd..3ed043cdb 100644
--- a/libraries/navigation_header.inc.php
+++ b/libraries/navigation_header.inc.php
@@ -10,8 +10,6 @@
  *
  */
 if (empty($query_url)) {
-    $db     = ! isset($db)      ? '' : $db;
-    $table  = ! isset($table)   ? '' : $table;
     $query_url = PMA_generate_common_url($db, $table);
 }