[php] The character encoding of the HTML document was not declared

Well when you post, the browser only outputs $title - all your HTML tags and doctype go away. You need to include those in your insert.php file:

<!DOCTYPE html PUBLIC"-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<title>insert page</title></head>
<body>
<?php 

   $title = $_POST["title"];
   $price = $_POST["price"];

  echo $title;


 ?>  
</body>
</html>