diff --git a/adminer/drivers/mongo.inc.php b/adminer/drivers/mongo.inc.php
index ebacdc1f..2029f08b 100644
--- a/adminer/drivers/mongo.inc.php
+++ b/adminer/drivers/mongo.inc.php
@@ -328,9 +328,9 @@ if (isset($_GET["mongo"])) {
 			$limit = min(200, max(1, (int) $limit));
 			$skip = $page * $limit;
 			try {
-				return new Result($this->_conn->_link->executeQuery("$connection->_db_name.$table", new \MongoDB\Driver\Query($where, array('projection' => $select, 'limit' => $limit, 'skip' => $skip, 'sort' => $sort))));
+				return new Result($this->_conn->_link->executeQuery($this->_conn->_db_name . ".$table", new \MongoDB\Driver\Query($where, array('projection' => $select, 'limit' => $limit, 'skip' => $skip, 'sort' => $sort))));
 			} catch (Exception $e) {
-				$connection->error = $e->getMessage();
+				$this->_conn->error = $e->getMessage();
 				return false;
 			}
 		}
diff --git a/adminer/include/functions.inc.php b/adminer/include/functions.inc.php
index e8bedb07..070bfe64 100644
--- a/adminer/include/functions.inc.php
+++ b/adminer/include/functions.inc.php
@@ -1311,6 +1311,7 @@ function slow_query($query) {
 	$db = $adminer->database();
 	$timeout = $adminer->queryTimeout();
 	$slow_query = $driver->slowQuery($query, $timeout);
+	$connection2 = null;
 	if (!$slow_query && support("kill") && is_object($connection2 = connect($adminer->credentials())) && ($db == "" || $connection2->select_db($db))) {
 		$kill = $connection2->result(connection_id()); // MySQL and MySQLi can use thread_id but it's not in PDO_MySQL
 		?>
@@ -1321,8 +1322,6 @@ var timeout = setTimeout(function () {
 }, <?php echo 1000 * $timeout; ?>);
 </script>
 <?php
-	} else {
-		$connection2 = null;
 	}
 	ob_flush();
 	flush();
@@ -1422,11 +1421,11 @@ function edit_form($table, $fields, $row, $update) {
 	?>
 <form action="" method="post" enctype="multipart/form-data" id="form">
 <?php
+	$first = 0;
 	if (!$fields) {
 		echo "<p class='error'>" . lang('You have no privileges to update this table.') . "\n";
 	} else {
 		echo "<table class='layout'>" . script("qsl('table').onkeydown = editingKeydown;");
-		$first = 0;
 		foreach ($fields as $name => $field) {
 			echo "<tr><th>" . $adminer->fieldName($field);
 			$default = $_GET["set"][bracket_escape($name)];
diff --git a/adminer/select.inc.php b/adminer/select.inc.php
index 23658290..ab94ce7e 100644
--- a/adminer/select.inc.php
+++ b/adminer/select.inc.php
@@ -81,9 +81,8 @@ if ($_POST && !$error) {
 			. convert_fields($columns, $fields, $select)
 			. "\nFROM " . table($TABLE);
 		$group_by = ($group && $is_group ? "\nGROUP BY " . implode(", ", $group) : "") . ($order ? "\nORDER BY " . implode(", ", $order) : "");
-		if (!is_array($_POST["check"]) || $primary) {
-			$query = "SELECT $from$where_check$group_by";
-		} else {
+		$query = "SELECT $from$where_check$group_by";
+		if (is_array($_POST["check"]) && !$primary) {
 			$union = array();
 			foreach ($_POST["check"] as $val) {
 				// where is not unique so OR can't be used
diff --git a/adminer/user.inc.php b/adminer/user.inc.php
index 5243ea3b..8dd50289 100644
--- a/adminer/user.inc.php
+++ b/adminer/user.inc.php
@@ -120,8 +120,8 @@ if ($_POST && !$error) {
 
 page_header((isset($_GET["host"]) ? lang('Username') . ": " . h("$USER@$_GET[host]") : lang('Create user')), $error, array("privileges" => array('', lang('Privileges'))));
 
-if ($_POST) {
-	$row = $_POST;
+$row = $_POST;
+if ($row) {
 	$grants = $new_grants;
 } else {
 	$row = $_GET + array("host" => get_val("SELECT SUBSTRING_INDEX(CURRENT_USER, '@', -1)")); // create user on the same domain by default