What is the potential issue with updating a database value in PHP after performing a calculation?

The potential issue with updating a database value in PHP after performing a calculation is that the calculation may not be accurate if the database value is updated before the calculation is completed. To solve this issue, it is important to first retrieve the original database value, perform the calculation, and then update the database with the new calculated value.

// Retrieve the original database value
$query = "SELECT value FROM table WHERE id = 1";
$result = mysqli_query($connection, $query);
$row = mysqli_fetch_assoc($result);
$originalValue = $row['value'];

// Perform the calculation
$newValue = $originalValue + 10;

// Update the database with the new calculated value
$updateQuery = "UPDATE table SET value = $newValue WHERE id = 1";
mysqli_query($connection, $updateQuery);