cache_api.php

<?php
use Psr\SimpleCache\CacheInterface;

interface Api {
    
    public function get(array $data): mixed;
}

class CachedApi implements Api
{
    public function __construct(
        private Api $inner,
        private CacheInterface $cache
    ){}

    public function get(array $data): mixed
    {
        $key = $this->calculateKey($data);
        if ($this->cache->has($key)) {
            return $this->cache->get($key);
        }
        $result = $this->inner->get($data);
        $this->cache->set($key, $result, 3600);

        return $result;
    }

    private function calculateKey(array $data): string {return ''; /* Implement a key calculation based on $data */ }
}

class CachedApiTest extends \PHPUnit\Framework\TestCase
{

    public function testCacheOnlyFetchesOnce()
    {
        // In memory implementation of CacheInterface
        $cache = new ArrayCache();

        $inner = $this->createMock(Api::class);
        $inner->expects($this->once())->method('get')->willReturn(['result']);
        $cachedApi = new CachedApi($cache, $inner);

        $this->assertEquals(['result'], $cachedApi->get(['param' => 'value']));
        $this->assertEquals(['result'], $cachedApi->get(['param' => 'value']));
        $this->assertEquals(['result'], $cachedApi->get(['param' => 'value']));
    }
}