HTML

display success message after form submit in php

<div class="alert alert-success">
  <strong>Success!</strong> Indicates a successful or positive action.
</div>

<div class="alert alert-success alert-dismissible">
  <a href="#" class="close" data-dismiss="alert" aria-label="close">&times;</a>
  <strong>Success!</strong> Indicates a successful or positive action.
</div>

php alert message after submit

// Add alert script in php like
 echo "<script>alert('data saved succesfully');</script>";