PHP和MySQL：While循环

Question

首先，我是PHP和MySQL的新手，因此我仍然会按程序​​进行编码。

我正在开发一种应用程序，该应用程序可以进行交易并在一定的到期日向以前进行捐赠的用户支付应付款。 我有一个功能knapSolveFast2解决了背包问题（其中，数据库中的一组交易金额加在一起，到期日到期的用户应得的金额）。 目前，我的演示数据库如下所示：

如果我当前的日期（现在）= 2017-04-03 11:36:03 = CAST(NOW() AS DATETIME) ，则我的应用程序应遍历数据库，从tran_date maturity_date >= 1 month的tran_date （即WHERE maturity_date <= CAST(NOW() AS DATETIME) ）。 以发现每个用户和配对他们在while循环支付给其他用户tran_amt在其数据库tran_amt总结了至到期的用户发现due_amount使用背包功能knapSolveFast2 。

问题 ：在使用第一个while loop找到具有到期付款日期的用户（2个用户）之后，我试图运行一个内部while循环以将每个用户与tran_amt为所获取用户的到期金额的其他用户tran_amt 。 这里的问题是，内部while循环仅针对发现的第一个用户运行，而不适用于第二个用户。

编码

<?php
            $servername = "localhost";
            $username = "root";
            $password = "";
            $dbname = "test";

            $connect = @mysqli_connect($servername, $username, $password, $dbname);

            if (mysqli_connect_errno()) {

              die("<pre><h1>Sorry, we are experiencing a little Downtime!</h1></pre>");

            } 

            //include the match controller containing the knapSolveFast2 function
            include('controller/match.php');

            //UPDATE `pendingpair`SET `maturity_date`= DATE_ADD(`tran_date`, INTERVAL 1 MONTH)

            //select user to be paid
            $sql = "SELECT `user_id`, `due_payment` FROM `pendingpair` where `maturity_date` <= CAST(NOW() AS DATETIME) ORDER BY `id` ASC";

            $queryRun = mysqli_query($connect, $sql);
            $num_rows = mysqli_num_rows($queryRun);

            if ($num_rows > 0) {

                while ($row = mysqli_fetch_assoc($queryRun)) {

                    $user_id_due = $row['user_id'];
                    $user_amt_due = $row['due_payment'];

                    print_r($row);

                    /* Perform queries to select users to pay $user_id_due the sum of $user_amt_due; Where:
                    - user to be paid, $user_id_due, is not included in the pairing logic
                    - transacton payment to be chosen, ph_conf = 1,  has been confirmed
                    - transaction has not yet been paired for payment, tran_paired_status = 0
                    - transactions have not been flaged for fake POP (proof of Payment),  `ph_denied_fpop`= 0

                    */

                    $fetchQuery = "SELECT `tran_inv`, `tran_amt`, `user_id` FROM `pendingpair`WHERE `tran_amt` <= {$user_amt_due} && `user_id` != {$user_id_due} && `ph_conf`=1 && `tran_paired_status` = 0 && `ph_denied_fpop`=0 ORDER BY `id`";

                    $m = array(); // Match Memo items array
                    $picked_trans = array();
                    $numcalls = 0; // number of calls made to get Match        
                    $tran_inv = array();
                    $tran_amt = array();
                    $user_id = array();

                    //run query and throw users that fit the criteria into an array
                    if ($queryRun = mysqli_query($connect, $fetchQuery)) {

                         //check if data was pulled
                         if (mysqli_num_rows($queryRun) != NULL) {

                            //grab data from array and insert it into an array
                            while ($row = mysqli_fetch_assoc($queryRun)) {

                                //Populate Arrays to be used
                                $tran_amt[] = $row['tran_amt'];
                                $tran_inv[] = $row['tran_inv'];
                                $user_id[] = $row['user_id'];

                            }
                        }
                    }

                    ## Solve
                    list ($m4,$pickedItems) = knapSolveFast2($tran_amt, $tran_amt, sizeof($tran_amt) -1, $user_amt_due, $m);

                    # Display Result 
                    echo "<b><br><br>Invoice:</b><br>".join(", ",$tran_inv)."<br>";
                    echo "<b>Tran Amt:</b><br>".join(", ",$tran_amt)."<br>";
                    echo "<b>User_id:</b><br>".join(", ",$user_id)."<br>";
                    echo "<b>Max Value Found:</b><br>$m4 (in $numcalls calls)<br>";


                }
            }
            ?>

第一个while循环的结果是找到具有正确到期日期条件的用户：

            Array
            (
                [user_id] => 9
                [due_payment] => 150
            )
            Array
            (
                [user_id] => 2
                [due_payment] => 150
            )

这意味着有2位用户到期。 但尝试循环这些用户。 永远不会找到第二个用户的匹配...只有第一个用户的匹配。

    Array
    (
        [user_id] => 9
        [due_payment] => 150
    )


    Invoice:
    1102, 9022, 9113, 9029, 9116
    Tran Amt:
    100, 50, 100, 50, 50
    User_id:
    2, 5, 8, 5, 7
    Max Value Found:
    150 (in 19 calls)

请帮助我找出我所缺少的。 Thaaaaank你:)

Answer 1

您的问题是您将变量称为同一件事。

如果您看：

while ($row = mysqli_fetch_assoc($queryRun))  //External loop

在该循环中，您还有另一个

while ($row = mysqli_fetch_assoc($queryRun))   //Internal loop

因此，您在内部循环中使用的外部循环内部的变量实际上会覆盖外部循环变量，因此，当需要第二次运行外部循环时，代码认为它已经完成，因为它引用了内部循环变量

要解决此问题，必须重命名用于内部循环的变量

Answer 2

注释SECOND_对于queryRun和该行都尝试此操作：

if ($SECOND_queryRun = mysqli_query($connect, $fetchQuery)) {

                     //check if data was pulled
                     if (mysqli_num_rows($SECOND_queryRun) != NULL) {

                        //grab data from array and insert it into an array
                        while ($SECOND_row = mysqli_fetch_assoc($SECOND_queryRun)) {

                            //Populate Arrays to be used
                            $tran_amt[] = $SECOND_row['tran_amt'];
                            $tran_inv[] = $SECOND_row['tran_inv'];
                            $user_id[] = $SECOND_row['user_id'];

                        }
                    }
                }