PHP表单处理用url中的POST数据重定向

在第一次提交时，这将返回用户到索引，其中POST数据仍在URL中。在第二次提交url中的数据时，它将返回错误或处理邮件。我不确定到底是什么导致了这一点。

<?php
if(!isset($_POST['submit']))
{
//This page should not be accessed directly. Need to submit the form.
echo "error; you need to submit the form!";
}
$name = $_POST['name'];
$company = $_POST['company'];
$project = $_POST['project'];
$email = $_POST['email'];
$phone = $_POST['phone'];
$message = $_POST['message'];
unset($_POST);
//Validate first
if(empty($name)||empty($email)) 
{
echo "Name and email are mandatory!";
exit;
}
if(IsInjected($email))
{
echo "Bad email value!";
exit;
}
$email_from = 'wevans.evansweb@gmail.com';
$email_subject = "New Contact Request";
$email_body = "You have received a new message from $name.'n
email: $email'n
company: $company'n
project: $project'n
phone: $phone'n
message: $message'n";
$to = 'wevans.evansweb@gmail.com';
$headers = "From: $email_from 'r'n";
mail($to,$email_subject,$email_body,$headers);
//done. redirect to thank-you page.
header('Location: index.html');

// 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;
  }
}
?>