我在页面中直接使用PHP mail（）创建了一个联系人表单。它成功地通过电子邮件将te联系信息发送给收件人。但是，它不会前进到header（）中标识的确认页面，并输出以下错误：

警告：无法修改标题信息-标题已由/home/redacted/redacted.com/wp-content/themes/diner/includes/theme-functions.php:752）发送。com/wp内容/主题/餐厅/页面。php在线163

关于如何解决这个问题，有什么建议或资源链接吗？

<?php
function spamcheck($field)
  {
  //filter_var() sanitizes the e-mail
  //address using FILTER_SANITIZE_EMAIL
  $field=filter_var($field, FILTER_SANITIZE_EMAIL);

  //filter_var() validates the e-mail
  //address using FILTER_VALIDATE_EMAIL
  if(filter_var($field, FILTER_VALIDATE_EMAIL))
    {
    return TRUE;
    }
  else
    {
    return FALSE;
    }
  }

if (isset($_REQUEST[\'contact_email\']))
  {//if "email" is filled out, proceed

  //check if the email address is invalid
  $mailcheck = spamcheck($_REQUEST[\'contact_email\']);
  if ($mailcheck==FALSE)
    {
    echo "Invalid input";
    }
  else
    {//send email
    $inquirer_name = $_REQUEST[\'contact_name\'] ;
    $email = $_REQUEST[\'contact_email\'] ;
    wp_mail(
"[email protected]",
"Subject: Test contact",
"Name: $inquirer_name
Email: $email "
);
header("Location:http://redacted.com/contact-confirmed");
    }
  } else { //if "email" is not filled out, display the form ?>

<form method="post" action="http://redacted.com/contact">
<ul>
<li>First Name: <input name="contact_name" type="text" /></li>
<li>Email: <input name="contact_email" type="text" /></li>
<li><input type=\'submit\' /></li>
</ul>

<?php } ?>