PHP：POST变量到下一页错误

Question

我有一个简单的问题。 test.php的

<form name ="myForm" method="post" id="back" action="homepage1.php">
   Auth:<select name="category" id="category">
   <option>1234</option>
   <option>4231</option>
   <option selected="selected">

   </option>
   <option></option>
   </select>
   <input type="submit" id ="submit" name="submit" value = "submit" >
</form>

homepage1.php

<?php
    $selectedid = $_POST['category'];
    echo $selectedid;
?>

错误：未定义的索引：第121行的E：\ xampp \ htdocs \ website \ homepage1.php中的类别

任何人都可以告诉我我做错了什么。谢谢

Answer 1

1.Select-box选项没有任何value属性，所以添加如下： -

<form name ="myForm" method="post" id="back" action="homepage1.php">
   Auth:<select name="category" id="category">
        <option value="1234">1234</option><!-- add option value-->
        <option value="4231">4231</option>
   </select>
<input type="submit" id ="submit" name="mysubmit" value = "submit" ><!--change button name to something else -->
</form>

2.更改homepage1.php代码如下： -

<?php

//comment these two error reporting lines when code started working fine
error_reporting(E_ALL);
ini_set('display_errors',1);

if(!empty($_POST['category'])){
    $selectedid = $_POST['category'];
    echo $selectedid;
}
?>

Answer 2

添加提交按钮以发布表单，如果您只是重定向或打开homepage1.php而不发布，您将收到此错误，因为$ _POST表单中没有“类别”。你可以看到更多关于POST and how prevent empty post here的信息。

您还需要为这些选项添加值，如下所示：

<option value="4231">4231</option>

更完整的例子：

HTML：

 <form name ="myForm" method="post" id="back" action="homepage1.php">
   Auth:
   <select name="category" id="category">
      <option value="1234">1234</option>
      <option value="4231">4231</option>
      <option value="45698" selected="selected">45698</option>
      <option value="9874">9874</option>
   </select>
   <input type="submit" name="btnSubmit" value = "Go!" >
</form>

PHP：

//Check if its a empty post
if(!empty($_POST)){
        $selectedid = $_POST['category'];
        echo $selectedid;
}