Question

The thing is this:
For all the subscribed players there is a random formula based on their skills. This formula has to be updated several times in a row with a sleep between it. The Calculation has to be a sum of the previous calculations + the new ones.
The thing is that I want to update the Calculation in my table wedstrijdresultaten, but because the calculation is in a while loop I cannot use

$Calculation = $row['Calculation'] + ($Skills / 35)*rand($Skills, 100);

This is what I thought would work, but it doesn’t:

$sqlUpdate = "UPDATE wedstrijdresultaten  SET Calculation='".$row['Calculation'] + ($Skills / 35)*rand($Skills, 100)."'";

Answer 1

See “Operator Precedence” in the PHP documentation. + and . have equal precedence, and are left-associative, so this:

"..." . a + b . "..."

means this:

(("..." . a) + b) . "..."

You need to use parentheses to force the addition to be performed before the concatenation:

$sqlUpdate = "UPDATE wedstrijdresultaten  SET Calculation='"
              . ($row['Calculation'] + ($Skills / 35)*rand($Skills, 100))
              . "'";