memoize.php

<?php

class Label
{
    private $label;

    public function __construct(string $label)
    {
        $this->label = $label;
    }

    public function getText(): string
    {
        return $this->label;
    }
}

function pluralizeLabel(Label $label): string
{
    $entries = [
        'angle' => ['singular' => 'angle', 'plural' => 'angles'],
        'issue' => ['singular' => 'issue', 'plural' => 'issues']
    ];

    echo "Reading from database. \n";

    $text = strtolower($label->getText());
    return $entries[$text]['plural'];
}

function memoize(callable $fn, callable $serialize = null): callable
{
    $serialize = $serialize ?: 'serialize';

    return function (...$args) use ($fn, $serialize) {
        static $cache = [];
        $key = $serialize($args);
        
        return $cache[$key] ?? ($cache[$key] = $fn(...$args));
    };
}

// Example
$issue = new Label('Issue');

// use the closure instead of serialize to get the key.
$pluralize = memoize('pluralizeLabel', function(array $args) {
    $label = $args[0];
    return $label->getText();
});

// connects to the database, finds record, returns plural.
echo "First call: \n";
echo $pluralize($issue) . "\n\n"; // => issues

// Gets the value from the cache instead
echo "Second call: \n";
echo $pluralize($issue) . "\n\n"; // => issues

// Gets the value from the cache instead
echo "Third call: \n";
echo $pluralize($issue) . "\n\n"; // => issues