Variable Table Name in sql SELECT FROM [duplicate]

How can I use a php variable, $dbLoc, after FROM in this sql query?

$dbLoc=$_SESSION['dBase'];
$result = mysqli_query($conn, 'SELECT SUM(gradeV) AS value_sum FROM $dbLoc'); 
$row = mysqli_fetch_assoc($result); 
$gradeV = $row['value_sum'];