Php，如何在表单提交后发送确认邮件

Hi there and thank you very much for your help in advance!

I'd like to send a custom confiramtion email to a user after form submission.

I have no idea how to set this up in my php file. I am a very beginner - sorry for a nooby question :-/ Thanks!!

<?php
if(isset($_POST['email'])) {

    // CHANGE THE TWO LINES BELOW
    $email_to = "christian@diamond-precision-studio.com";

    $email_subject = "website html form submissions";


    function died($error) {
        // your error code can go here
        echo "We are very sorry, but there were error(s) found with the form you submitted. ";
        echo "These errors appear below.<br /><br />";
        echo $error."<br /><br />";
        echo "Please go back and fix these errors.<br /><br />";
        die();
    }

    // validation expected data exists
    if(!isset($_POST['first_name']) ||

        !isset($_POST['email']) ||
        !isset($_POST['budget']) ||
        !isset($_POST['message'])) {
        died('We are sorry, but there appears to be a problem with the form you submitted.');       
    }

    $first_name = $_POST['first_name']; // required

    $email_from = $_POST['email']; // required
    $budget = $_POST['budget']; // not required
    $message = $_POST['message']; // required

    $error_message = "";
    $email_exp = '/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$/';
  if(!preg_match($email_exp,$email_from)) {
    $error_message .= 'The Email Address you entered does not appear to be valid.<br />';
  }
    $string_exp = "/^[A-Za-z .'-]+$/";
  if(!preg_match($string_exp,$first_name)) {
    $error_message .= 'The First Name you entered does not appear to be valid.<br />';
  }

  if(strlen($message) < 2) {
    $error_message .= 'The Comments you entered do not appear to be valid.<br />';
  }
  if(strlen($error_message) > 0) {
    died($error_message);
  }
    $email_message = "Form details below.

";

    function clean_string($string) {
      $bad = array("content-type","bcc:","to:","cc:","href");
      return str_replace($bad,"",$string);
    }

    $email_message .= "First Name: ".clean_string($first_name)."
";

    $email_message .= "Email: ".clean_string($email_from)."
";
    $email_message .= "Budget: ".clean_string($budget)."
";
    $email_message .= "Message: ".clean_string($message)."
";


// create email headers
header( "Location: https://www.diamond-precision-studio.com/new-website/thank-you.html" );

$headers = 'From: '.$email_from."
".
'Reply-To: '.$email_from."
" .
'X-Mailer: PHP/' . phpversion();
@mail($email_to, $email_subject, $email_message, $headers);


?>

<!-- place your own success html below -->



<?php
}
die();
?>

this line:

header( "Location: https://www.diamond-precision-studio.com/new-website/thank-you.html" );

will redirect your script to another page BEFORE you call mail function. It means, mail will never be executed. So, remove it.