Memoizing-fibonacci-function-in-php

class Fib{
    //$memo and fibonacciMemo are static members
    static $memo = array();
    static function fibonacciMemo($n) {
      if(array_key_exists($n, static::$memo)) {
        return static::$memo[$n];
      }
      else {
        if($n > 1) {
          $result = static::fibonacciMemo($n-1) + static::fibonacciMemo($n-2);
          static::$memo[$n] = $result;
          return $result;
        }
        return $n;
      }
    }
}

//Using the same method by Edd Mann to benchmark 
//the results

$start = microtime(true);
Fib::fibonacciMemo(10);
echo sprintf("%f\n", microtime(true) - $start);
//outputs 0.000249

$start = microtime(true);
Fib::fibonacciMemo(10);
echo sprintf("%f\n", microtime(true) - $start);
//outputs 0.000016 (now with memoized fibonacci)

//Cleaning $memo
Fib::$memo = array();
$start = microtime(true);
Fib::fibonacciMemo(10);
echo sprintf("%f\n", microtime(true) - $start);
//outputs 0.000203 (after 'cleaning' $memo)

https://stackoverflow.com/questions/28870968/memoizing-fibonacci-function-in-php