form with html entities in php

<?php

if(isset($_POST['name'])&&isset($_POST['age']))
{
  $name=$_POST['name'];
  $age=$_POST['age'];
  if(!empty($name)&&!empty($age))
  {
   echo '<center>name :<b>'.$name.'</b> age :<b>' .$age.'</b><br><br></center>';
  }
  else
  {
   echo '<center><b>you not filled both fields</b><br><br></center>';
  }

}

?>
<center><form action="form.php" method="POST">

               NAME :<input type="text" name="name">

               AGE  :<input type="text" name="age">

                <input type="submit" value="submit">
</form></center>

output :

1)if you  filled all fields output displays that is  you entered data

other wise it gives a message as " you not filled both fields "
2) if you give html entities then it also displays as it is