php sum列在多个表中，并作为一个总数返回

Question

I have a php code below that sum up the column going through multiple tables and return 3 separate total amounts after the query is done since I have 3 tables. If I want to sum up those 3 total amounts into one, in what ways do I need to change the code to accomplish that?

foreach($result as $row) {
  $stmt1 = $DB_CON_C->prepare("SELECT SUM(total_fee) AS total_amount FROM `".$row['files']."`");
  $stmt1->execute();
  $sum1 = $stmt1->fetch(PDO::FETCH_ASSOC);

  echo $sum1['total_amount'];
}

Answer 1

Try something like this:

$totalAmount = 0;

foreach($result as $row) {
    $stmt1 = $DB_CON_C->prepare("SELECT SUM(total_fee) AS total_amount FROM `".$row['files']."`");
    $stmt1->execute();

    $sum1 = $stmt1->fetch(PDO::FETCH_ASSOC);

  totalAmount += $sum1['total_amount'];
}

echo $totalAmount;

Just create a variable outside of the loop's scoop and add up to it.

Answer 2

Try something like this. Create a variable outside the loop, then increment it per loop.

$grandTotal = 0;
foreach($result as $row) {
  $stmt1 = $DB_CON_C->prepare("SELECT SUM(total_fee) AS total_amount FROM `".$row['files']."`");
  $stmt1->execute();
  $sum1 = $stmt1->fetch(PDO::FETCH_ASSOC);

  $grandTotal = $grandTotal +  $sum1['total_amount'];
}
echo $grandTotal;

Not sure if this works, but you get the idea.