Fibonacci sequence generator class, a play with PHP7 features.

Fibonacci.php

<?php
declare(strict_types=1);

/**
 * Fibonacci sequence generator, a play with PHP7 features.
 * @author Lawrence Cherone <cherone.co.uk>
 */
class Fibonacci {
    
    private $sequence = [];
    
    /**
     * Run/build sequence
     * 
     * @param int $start  - Starting number in sequence
     * @param int $length - Length of sequence
     * @return array
     */
    public function run (int $start, int $length = 10): array
    {
        $this->sequence = [
            0, $start
        ];
        try {
            for ($i=2; $i < $length; $i++) {
                $this->sequence[$i] = $this->next(
                    $this->sequence[$i-2],
                    $this->sequence[$i-1]
                );
            }
        } catch (\Exception $e) {
            
        }
        
        return $this->sequence;
    }
    
    /**
     * Determine next number in sequence
     * 
     * @param [int [, int]] Previous, Current ints in sequence
     * @return int
     */
    public function next (int ...$seq): int 
    {
        $next  = 0;
        $next += \end($seq);
        $next += \prev($seq);
        
        if ($next > PHP_INT_MAX) {
            throw new \Exception('Max limit reached');
        }
        
        return $next;
    }

    /**
     * The sum of all sequence
     * 
     * @return mixed
     */
    public function sum ()
    {
        return \array_sum($this->sequence);
    }
    
    /**
     * Sequence as string
     * 
     * @return string
     */
    public function __toString(): string
    {
        return \implode('-', $this->sequence);
    }
}

$fibonacci = new \Fibonacci();
$fibonacci->run(1, 25);

// 0-1-1-2-3-5-8-13-21-34-55-89-144-233-377-610-987-1597-2584-4181-6765-10946-17711-28657-46368
echo $fibonacci;

// 121392
echo $fibonacci->sum();