How to convert number in billions to a smaller string of comparison?

Imagine that you have an exercise in the following aspect, I need to get an array with random integers, the largest number that is between the ranges.

For example, I have an array: array(2, 8, 4);

Based on this idea, I have the following code structure:

<?php

class VerifyNumbers
{

    private $arr = array();

    public function __construct(array $arr)
    {
        $this->arr = $arr;
    }

    public function verifyMaxIntersectionFromArray()
    {
        $collection = array();

         sort($this->arr);

        for ($i= 0; $i < count($this->arr); $i++) {
            if (isset($this->arr[$i + 1])) {
               $collection[] = ($this->arr[$i + 1] - $this->arr[$i]);
            }
        } 
        return max($collection);
    }

}

$verifyNumber = new VerifyNumbers(array(100, 3000, 4000, 25, 540, 20, 200, 300));
$maxIntersection = $verifyNumber->verifyMaxIntersectionFromArray();

echo $maxIntersection;

The question I ask is, and if in case, would I have input values in this array that would exceed 4 billion, or even larger, because there could be negative numbers, which would double, the interval, as I could convert these input numbers into a smaller, readable string, because in PHP 5, an invalid digit is passed to octal integer (for example, 8 or 9), the rest of the number will be ignored.