获取数据无法通过

This is my HTML form:

  <form action='buddy_update.php'>
  <input type='text' name='buddy1' required='' placeholder='Player ID / E-mail'>
  <input type='hidden' name='id' value=''%".$id."%''>
  <input type='submit' value='Request Buddy #1!'>
  </form>

This is my PHP on buddy_update

<?php
include 'credentials.php';
$id=$_GET['id'];
$buddy1=$_GET['buddy1'];

// Create connection
$conn = mysqli_connect($servername, $username, $password, $dbname);
// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

$id=$_GET['id'];
$buddy1=$_GET['buddy1'];

$sql = "UPDATE buddy SET buddy1_id = '".$buddy1."' WHERE main_player = '".$id."'";

if (mysqli_query($conn, $sql)) {
echo $id;
    echo $buddy1;
} else {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}

mysqli_close($conn);
?>

$buddy1 comes through absolutely fine but $id doesn't.

For what it's worth I have also changed the value='' to a plain text input on the HTML form and it still doesn't work. The output in the PHP form is still blank.

EDIT No idea why I've defined variables twice! Took the one out but still same problem

There are few things to consider:

1. Your html form should be in .php file

2. Your form needs to have method='get', <form action='buddy_update.php' method='GET'>

3. <input type='hidden' name='id' value="<?php if(isset($_GET['id'])){echo $_GET['id'];}?>"> in case you are getting this GET variable`

Your code can't access the $id value. Why don't you try this

<input type='hidden' name='id' value='<?php echo $id ?>'>

assuming you define $id above this statement

It seems you have defined form in php.Since $id states that variable is defined in php. so you can try to replace your code with some thing like below code

echo  "<form action='buddy_update.php'>
  <input type='text' name='buddy1' required='' placeholder='Player ID / E-mail'>
  <input type='hidden' name='id' value='".$id."'>
  <input type='submit' value='Request Buddy #1!'>
  </form>";

You have to ensure that the input (hidden) always has a value. Else it will throw invalid index error. $id is not getting any value here: