DesignPatternsPHP/Behavioral/Specification/NotSpecification.php

<?php
declare(strict_types=1);

namespace DesignPatterns\Behavioral\Specification;

class NotSpecification implements Specification
{
    /**
     * @var Specification
     */
    private $specification;

    public function __construct(Specification $specification)
    {
        $this->specification = $specification;
    }

    public function isSatisfiedBy(Item $item): bool
    {
        return !$this->specification->isSatisfiedBy($item);
    }
}