如何从下拉菜单中的值查询行 PHP

Question

下面是我的代码。我想查询一行并在我从下拉菜单中 select 后立即打印（onchange）。请帮忙。谢谢。

<?php

$conn = new mysqli('localhost', 'root', 'jared17', 'hbadb') 
or die ('Cannot connect to db');

$result = $conn->query("select * from students");

echo "<html>";
echo "<body>";
echo "<form method = POST>";
echo "<select name = 'Students' onchange=this.form.submit()>";

while ($row = $result->fetch_assoc()) {

              unset($LRN, $First, $Last);
              $LRN = $row['LRN'];
              $First = $row['First_Name'];
              $Last = $row['Last_Name']; 
              echo '<option value="'.$First.'">'.$First.' '.$Last.'</option>';}

echo "</select>";
echo "<input type='submit' name='submit' value='Show'>";
    if(isset($_POST['submit'])) {
    echo "*******I WANT TO QUERY THE ROW I SELECTED IN DROPDOWN MENU****";
    }
echo "</form>";
echo "</body>";
echo "</html>";
?>

Answer 1

就这么简单

if(isset($_POST['submit'])) {
    echo $_POST['Students'];
    }

编辑： 最好使用 filter_input() 函数而不是直接访问全局数组。在这种情况下，它将是

$submit = filter_input(INPUT_POST,'submit');
$students = filter_input(INPUT_POST,'Students');

if(isset($submit)) {
    echo $students;
}

Example

Answer 2

你可以直接这样做：

if(isset($_POST['submit'])) {
   echo $_POST['Students'];
}

或者您可以使用print_r来解决您的困惑：

print_r($result);

如何从下拉菜单中的值查询行 PHP

How to query row from a value from dropdown menu PHP

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