random-hex.php

<?php

interface RandomGeneratorInterface
{
    public function getString(int $length): string;
    public function getBytes(int $length): string;
}

class RandomFileReader implements RandomGeneratorInterface
{
    public function __construct(
        private $fh = null,
        string $path = '/dev/urandom',
    ) {
        if (!$this->fh) {
            $this->fh = fopen($path, 'r');
        }
    }

    public function getString(int $length): string
    {
        return bin2hex($this->getBytes($length));
    }

    public function getBytes(int $length): string
    {
        return fread($this->fh, $length);
    }
}

$rand = new RandomFileReader();
echo "random-hex: {$rand->getString(4)}\n";