可以'；t让php输出一个表单

我正在尝试用php制作一个函数表单。起初，我制作了一个"index.html"文件和另一个名为send.php的文件。但它不起作用。我还尝试在send.php中插入"echo"，结果成功了！因此，我将index.html转换为index.php，并将php代码放在其中，然后放在body结束标记（标记）之前，但它不起作用！所以我意识到错误在代码中，但我从互联网上复制了这些行，我对php不是很了解。有人能帮我吗？这是代码：

我检查了字段的name="是否正确。

<?php 
$name = ($_POST['name'];
$mail = ($_POST['mail'];
$budjet = ($_POST['budjet'];
$society = ($_POST['society'];
$message = ($_POST['message'];
$error = "Message sending failed";
$errorMessage = "Sorry your message can not be sent.";
//Validate first
if(empty($name)||empty($mail)||empty($budjet)||empty($society)||empty($message)) 
{
    echo "Please fill al the fields";
    header('Location: index.html');
}
//validate against any email injection attempts
if(IsInjected($email))
{
    echo "Bad email value";
    header('Location: index.html');
}
$msg = "Name : $name 'r'n"; 
$msg = "Mail : $mail 'r'n";
$msg = "Budjet: $budjet 'r'n";
$msg = "Society: $society 'r'n";
$msg = "Message : ".stripslashes($_POST['message'])."'r'n'n";
$msg = "User information 'r'n"; 
$msg = "User IP : ".$_SERVER["REMOTE_ADDR"]."'r'n"; 
$msg = "Browser info : ".$_SERVER["HTTP_USER_AGENT"]."'r'n"; 
$msg = "User come from : ".$_SERVER["SERVER_NAME"];
$recipient = "myemail@mail.com"; // Change the recipient email adress to your adrees  
$sujet =  "Mail da Contact di Hindeto";
$mailheaders = "From: $email'r'nReply-To: $email'r'nReturn-Path: $email'r'n";
if (!$error){
        $sending = mail($recipient, $sujet, $msg, $mailheaders); 
        if ($sending) {
                // If the message is sent we output a string to use it 
                echo "Sent"; 
            } else {
                // Display Error Message
                echo $errorMessage; 
            }
    } else {
        echo $error; // Display Error Message
    }

// Function to validate against any email injection attempts
function IsInjected($str)
{
  $injections = array('('n+)',
              '('r+)',
              '('t+)',
              '(%0A+)',
              '(%0D+)',
              '(%08+)',
              '(%09+)'
              );
  $inject = join('|', $injections);
  $inject = "/$inject/i";
  if(preg_match($inject,$str))
    {
    return true;
  }
  else
    {
    return false;
  }
}
?>