[Resolved]Call to undefined function Help

[308holes]

Hello need a little help I keep getting an error "Fatal error: Call to undefined function rating_avg()"

The function is in rating.php

<?php
function rating_avg($id)
{
  //sample code
  $A = $id;
  $B = "rating ";
  $C = $A + $B;
  return $C;
}
?>

The call page

<?php require('rating.php');//header
echo rating_avg($RPID);
?>