function mean ($a)
{
  //variable and initializations
  $the_result = 0.0;
  $the_array_sum = array_sum($a); //sum the elements
  $number_of_elements = count($a); //count the number of elements

  //calculate the mean
  $the_result = $the_array_sum / $number_of_elements;

  //return the value
  return $the_result;
}

$the_average = mean($a);

echo "a[0] = $a[0]<br>";
echo "a[1] = $a[1]<br>";
echo "a[2] = $a[2]<br>";
echo "the_average = $the_average<br>";

?>