Php 从每个字段的列中获取值，但返回NULL？

我试图从我的数据库中的列rounds中获取“rounds”的值。所以，我想得到每个辩论/帖子的字段值（1-5）。根据值/数字，它应该显示不同的内容。当我假定得到这个值时，它会说NULL，即使该辩论/帖子的db字段中的值是4。这不仅是一场辩论，而且对所有人都是如此。如何获取列中字段的实际值并将其分配给名为$rounds的变量。这个变量需要有每次辩论的值，而不仅仅是那个辩论

<?php
$servername = "";
$username = "";
$password = "";
$dbname = "";

$con = new mysqli($servername, $username, $password, $dbname);

if ($con->connect_error) {
    die("Connection failed: " . $con->connect_error);
}
else{
  $sql = "SELECT rounds FROM vf_Discussion";
    $result = $con->query($sql);

    $allRounds = $result->fetch_row();
    $rounds = $allRounds[0];

    var_dump($rounds);

}
   mysqli_close($con);

      $rounds1 =        '<h2 class="CommentHeading">Round 1 (Pro)</h2> <br> <h2 class="CommentHeading">Round 1 (Con) </h2>';

      $rounds2 =    '<h2 class="CommentHeading">Round 2 (Pro)</h2> <br> <h2 class="CommentHeading">Round 2 (Con)</h2>';

      $rounds3 =    '<h2 class="CommentHeading">Round 3 (Pro)</h2> <br> <h2 class="CommentHeading">Round 3 (Con)</h2>';

      $rounds4 =        '<h2 class="CommentHeading">Round 4 (Pro)</h2> <br> <h2 class="CommentHeading">Round 4 (Con)</h2>';

      $rounds5 =    '<h2 class="CommentHeading">Round 5 (Pro)</h2> <br> <h2 class="CommentHeading">Round 5 (Con)</h2>';

    foreach($allRounds as $rounds) {
        if ($rounds == 1) {
            echo $rounds1;
            foreach ($Sender->Data('Answers') as $Row) {
                $Sender->EventArguments['Comment'] = $Row;
                WriteComment($Row, $Sender, Gdn::Session(), 0);
            }
        }
        if ($rounds == 2) {
            echo $rounds1;
            echo $rounds2;
            foreach ($Sender->Data('Answers') as $Row) {
                $Sender->EventArguments['Comment'] = $Row;
                WriteComment($Row, $Sender, Gdn::Session(), 0);
            }
        }
        if ($rounds == 3) {
            echo $rounds1;
            echo $rounds2;
            echo $rounds3;
            foreach ($Sender->Data('Answers') as $Row) {
                $Sender->EventArguments['Comment'] = $Row;
                WriteComment($Row, $Sender, Gdn::Session(), 0);
            }
        }
        if ($rounds == 4) {
            echo $rounds1;
            echo $rounds2;
            echo $rounds3;
            echo $rounds4;
            foreach ($Sender->Data('Answers') as $Row) {
                $Sender->EventArguments['Comment'] = $Row;
                WriteComment($Row, $Sender, Gdn::Session(), 0);
            }
        }
        if ($rounds == 5) {
            echo $rounds1;
            echo $rounds2;
            echo $rounds3;
            echo $rounds4;
            echo $rounds5;
            foreach ($Sender->Data('Answers') as $Row) {
                $Sender->EventArguments['Comment'] = $Row;
                WriteComment($Row, $Sender, Gdn::Session(), 0);
        }
    }

    }
         ?>

---

您应该遍历对象

<?php







    $servername = "";
    $username = "";
    $password = "";
    $dbname = "";


    $con = new mysqli($servername, $username, $password, $dbname);

    if ($con->connect_error) {
        die("Connection failed: " . $con->connect_error);
    }
    else{
      $sql = "SELECT rounds FROM vf_Discussion";
        $result = $con->query($sql);


       while($row = mysql_fetch_array($result))
      {

          var_dump($row);
    }




    }

---

不起作用，您能提供另一个工作解决方案吗？可能重复