<?php

$sequence = array();

for ($i = 0; $i <= 100 ; $i++) { 
    if ( $i < 2 ) {
        $sequence[$i] = $i;         
    } else{
        $sequence[$i] = $sequence[$i - 1] + $sequence[$i - 2];          
    }       
}


function fibonacci($n){
    global $sequence;
    echo $sequence[$n];

};

fibonacci(100);