PHP SQL query wont work : I want to get the last time my database was updated, so i use this query in my PHP code:

    $query = mysqli_query($mysqli, "SELECT UPDATE_TIME
									FROM   information_schema.tables
									WHERE  TABLE_SCHEMA = 'map_db'
									AND TABLE_NAME = ".$objects_tab."");
			$lastUpdateTime = mysqli_fetch_array($query);
			echo "<div id ='lastUpdate'>".$lastUpdateTime."</div>";
For some reason the query wont work, does anyone know whats the problem?

It works when i do other queries so its not the $mysqli connect variable or the table name variable thats wrong. 

Thanks in advance! :)