PHP and MySQL error: Object of class mysqli_result could not be converted to string

Question

I am getting the error:

Object of class mysqli_result could not be converted to string.

Code:

Answer 1

You cannot directly output the result of a query. Use:

$sql = ("select sum(`memory`) AS memTotal from `server`");
// Show used memory
$result = mysqli_query($con, $sql);
echo $result->fetch_object()->memTotal;

The $result variable holds an object (of type mysqli_result), from which you can fetch the scalars you need to output.

Answer 2

$result is a result object. From thje manual for mysqli_query():

Returns FALSE on failure. For successful SELECT, SHOW, DESCRIBE or EXPLAIN queries mysqli_query() will return a mysqli_result object. For other successful queries mysqli_query() will return TRUE.