试图从php调用mysql存储过程

The php is called through ajax from a button on a different page and I'm trying to remove a column from my database. The code runs all the way through, but changes nothing in the database. The function works when run in mysql work bench. Any help is greatly appreciated!

$facNum = $_POST['facNum'];


$conn = mysqli_connect($dbhost, $dbuser, $dbpass);

if(! $conn ) {
  die('Could not connect: ' . mysqli_error());
 }


$sql = 'CALL makePositionVacant('. $facNum .')';


$retval = mysqli_query( $conn, $sql  );


$retval;


mysqli_close($conn);