Question

The following code gives me the following:

$getexpenses = "SELECT sum(expense_amount) FROM projects_expense WHERE project_id=$project_id";     
    $showexpenses = @mysqli_query ($dbc, $getexpenses); // Run the query.

    echo ' . $showexpenses . ';

Gives me a result of

' . $showexpenses . '

instead of the actual sum…

I’m sure it’s something simple I’m missing… thanks!

Answer 1

I added a call to mysqli_fetch_assoc($showexpenses)to make it fully functional.
I also sanitized $project_id to avoid injections and used an alias to make the sum accessible through an associative array.

$getexpenses = "SELECT SUM(`expense_amount`) as `sum_amount` FROM `projects_expense` WHERE `project_id`= ".intval($project_id);     
$showexpenses = mysqli_query ($dbc, $getexpenses);
$sums = mysqli_fetch_assoc($showexpenses);
$sum = $sums['sum_amount'];

echo $sum;

We could also have used mysqli_fetch_row like this:

$getexpenses = "SELECT SUM(`expense_amount`) FROM `projects_expense` WHERE `project_id`= ".intval($project_id);     
$showexpenses = mysqli_query ($dbc, $getexpenses);
$sums = mysqli_fetch_row($showexpenses);
$sum = $sums[0];

echo $sum;

The alias is not needed anymore since we know the first column (0) is a match.

NB: you probably also need to GROUP BY project_id if you want to use SUM()