<?php
declare(strict_types=1);

class LendingDesk {
    public function __construct(private int $available) { if ($available<0) throw new InvalidArgumentException("Negative stock"); }
    public function request(int $count): bool {
        if ($count<=0) throw new InvalidArgumentException("Positive request required");
        if ($count>$this->available) return false;
        $this->available-=$count; return true;
    }
    public function remaining(): int { return $this->available; }
}
$desk = new LendingDesk(6);
if (!$desk->request(4)) throw new RuntimeException("First request failed");
if ($desk->request(3)) throw new RuntimeException("Overdraw accepted");
if ($desk->remaining()!==2) throw new RuntimeException("Rejection changed stock");
echo "Reservation contract passed; 2 remain\n";