Returns the result of a supplied position in the Fibonacci Sequence

Fibonacci Position Function

<?php

/**
 * Returns the result of a supplied position in the Fibonacci Sequence.
 * 
 * @param mixed $n 
 * @access public
 * @return integer
 */
function get_fibonacci_position($n)
{
  if (!is_int($n))
  {
    throw new Exception($n . ' is not a number!');
  }

  // Starting the array on key 1 for semantic meaning (e.g. 1 = 1st)
  // Per Fibonacci spec, the 0 and 1 are given values.
  $result = array(
    1 => array(
      'last' => null,
      'previous' => null,
      'current' => 0,
    ),
    2 => array(
      'last' => null,
      'previous' => 0,
      'current' => 1,
    ),
  );

  /**
   * Since we've already defined the first two numbers in the sequence,
   * we only need to iterate from next entry.
   */
  $init_iterator = (count($result) + 1);

  for ($i = $init_iterator; $i < ($n + 1); ++$i)
  {
    $r =& $result;
    $r[$i]['last'] = $result[($i - 2)]['current'];
    $r[$i]['previous'] = $result[($i - 1)]['current'];
    $r[$i]['current'] = ($result[$i]['last'] + $result[$i]['previous']);
  }

  return $result[$n]['current'];
}