Remember: a simple Laravel / PHP volatile runtime cache

Remember.php

<?php

// save this file as ./app/Helpers/Remember.php

namespace App\Helpers {

    class Remember
    {
        public static array $that = [];
    }
}

// this is all - the part below is just usage example

namespace {

    use App\Helpers\Remember;

    // here we are back to the root namespace
    // https://www.php.net/manual/en/language.namespaces.definitionmultiple.php

    // example on how to process a given value/array and save results to the
    // volatile runtime cache (Remember::$that) and optionally regular cache

    if (! function_exists('pow_once')) {
        function pow_once(mixed $input, bool $distinct = true): mixed
        {
            if (!$is_array = is_array($input)) $input = [md5(json_encode($input)) => $input];

            foreach ($input as $key => $value) {
                // distinct [0 => some_value] and [0 => other_value]?
                // pass false to treat key as an idempotent cache key
                // and disregard what is sent as value on other calls
                $thing = $distinct ? md5($key . json_encode($value)) : $key;

                // you can retrieve data from runtime (volatile) cache only:
                $output[$key] ??= Remember::$that[$thing] ??= null;
                
                // or optionally use regular (persistent) cache as fallback:
                // $output[$key] ??= Remember::$that[$thing] ??= \Illuminate\Support\Facades\Cache::get($thing);

                if (is_null($output[$key])) {
                    // process $key/$value
                    $pow = ($is_array ? $key : $value) ** $value;

                    // feed the output array
                    $output[$key] = ($is_array ? $key : $value) . '^' . $value . ' = ' . $pow;

                    // save to regular (persistent) cache
                    // Cache::put($thing, $output[$key], now()->addMinutes(30));

                    // save to runtime (volatile) cache (suffix added for debug purposes)
                    Remember::$that[$thing] = $output[$key] . " (from cache)";
                }
            }

            // return the output array or 1st element when input is not array
            return $is_array ? $output : reset($output);
        }
    }
}