Meagram Solution (PHP)

Meagrams.php

<?php

declare(strict_types=1);

final class Meagrams
{
    /**
     * @var string[]
     */
    private $words;

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

    /**
     * @param string $word
     *
     * @return string[]
     */
    public function __invoke(string $word): array
    {
        $length = \strlen($word);

        $words = \array_filter($this->words, function ($word) use ($length) {
            return \strlen($word) === $length;
        });

        $characters = $this->characters($word);

        return \array_values(\array_filter($words, function ($word) use ($characters) {
            return 1 === $this->difference($characters, $this->characters($word));
        }));
    }

    private function characters(string $word): array
    {
        $characters = \str_split($word);

        \sort($characters);

        return $characters;
    }

    private function difference(array $charactersOne, array $charactersTwo): int
    {
        foreach ($charactersOne as $characterOne) {
            $key = \array_search(
                $characterOne,
                $charactersTwo,
                true
            );

            if (false !== $key) {
                unset($charactersTwo[$key]);
            }
        }

        return \count($charactersTwo);
    }
}