只能在$ _POST表单上使用foreach循环获取两个值

Question

在下面的代码中，我正在从数据库构建表单。问题是当使用foreach（$ _POST as $ response =＆gt; $ answer）时，我只得到两个变量$ response ['response']和$ response ['response_id']。为什么我无法获得更多，即回复，名称和价值？

// Question form
    echo "<style>.error{color: red;}
    </style>";
    echo '<form action="'.$_SERVER['PHP_SELF'].'" method="POST">';
    $legend = $responses[0]['category'];
    echo "<fieldset>";
    echo"<legend>$legend</legend>";
    foreach ($responses as $response) {
        if ($legend != $response['category']) {
            $legend = $response['category'];
            echo "</fieldset>"; 
            echo "<fieldset>";
            echo"<legend>$legend</legend>";
            var_dump($response);
        }   
        echo '<label '.($response['response'] == NULL ? 'class="error"' : '').'  for ="'.$response['response_id'].'">'.$response['name'].':</label>';
         echo   "Love <input ".($response['response'] == 1 ? 'checked = "checked"' :'')." type='radio' '.'id='".$response['response_id']."' name='".$response['topic_id']."' value='1'></input> or"; 
         echo   "Hate <input ".($response['response'] == 2 ? 'checked = "checked"':'')."type='radio' id='".$response['response_id']."' name='".$response['topic_id']."' value='2'></input><br />";

    }   
    echo "</fieldset>"; 
    echo"<br /><input type = 'submit' submit = 'submit'>";
    echo "</form>";


// php action on form

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
var_dump($_POST);
echo "post <br />";
foreach ($_POST as $response => $answer) {
    var_dump($_POST);
    $query = "UPDATE mismatch_response SET response = '$answer' WHERE response_id = '$response' ";
    mysqli_query($dbc, $query);



        //var_dump($answer);
}