在函数内添加新的数组键

Question

I have an array that is populated by a mysql_fetch_assoc. After the array is populated by the columns I want from the database, I would like to add another key to the array, using values that I obtain earlier in the function. I tried to accomplish this with a foreach loop, but my function is not returning the array. Where have I gone wrong?

//calculates payout 
function calculate_payout($id){
    $result = mysql_query("SELECT `result` FROM `bets` WHERE `id` = {$id}");
    echo mysql_error();
    $wager_total = mysql_query("SELECT SUM(`wager_amount`) AS `wager_total` FROM `wagers` WHERE `id` = '{$id}'");
    $correct_wager_total = mysql_query("SELECT SUM(`wager_amount`) AS `correct_wager_total` FROM `wagers` WHERE `id` = '{$id}' AND `wager_option` = '{$result}'");
    echo mysql_error();
    $incorrect_wager_total = $wager_total - $correct_wager_total;

    $sql = "    SELECT * FROM `wagers` WHERE `id` = '{$id}' AND `wager_option` = '{$result}'";
    echo mysql_error();
    $data = mysql_query($sql);

    $rows = array();
    while(($row = mysql_fetch_assoc($data)) !== false){
        $rows[] = array(
            'bet_id'         => $row['bet_id'],
            'id'             => $row['id'],
            'wager_amount'   => $row['wager_amount']
        );
    }

    foreach ($rows as $p_row){
        $payout = $p_row['wager_amount'] / $incorrect_wager_total;
        $payout = $p_row['wager_amount'] + $payout;
        $p_row['payout'] = $payout;
    }

    return $p_row;
}

Answer 1

The problem is that $p_row is a copy of the row in the array, so modifying it in the loop doesn't have any effect on the original array.

You can fix this by using a reference in the foreach:

foreach ($rows as &$p_row)

Or you can just do this as you're creating the $rows array in the while loop:

while ($row = mysql_fetch_assoc($data)) {
    $new_row = array(
        'bet_id'         => $row['id'],
        'id'             => $row['id'],
        'wager_amount'   => $row['wager_amount'],
        'payout'         => $row['wager_amount'] / $incorrect_wager_total + $row['wager_amount']
    );    

Also, your return statement is wrong, it should be return $rows; to return the whole array; return $p_row will just return the last row of the array.