Fibonacci Series

<?php


function fibonacci($old, $new, $end){

    static $start; 
                    /* Static Variable
                    *  In this function the value of static var value 
                    *  won't change
                    */
    $start = $start ?? 1;
    // ?? Ternary Operator Check start value

    if($start > $end){

        return;
    }
    $start++;

    echo $old." ";
    $_temp = $old+$new;  // $temp = 0+1
    $old = $new; // old = 1
    $new = $_temp; // new = 1

    fibonacci($old, $new, $end);
}

fibonacci(0,1,5);