#A magic memoization function

This package contains a once function. You can pass a callable to it. Here's quick example:

$myClass = new class() {
    public function getNumber(): int
    {
        return once(function () {
            return rand(1, 10000);
        });
    }
};

No matter how many times you run $myClass->getNumber() inside the same request you'll always get the same number.

#Are you a visual learner?

Under the hood, this package uses a PHP 8 Weakmap. In this video, you'll see what a weakmap is, together with a nice demo of the package.

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#Installation

You can install the package via composer:

composer require spatie/once

#Usage

The once function accepts a callable.

$myClass = new class() {
    public function getNumber(): int
    {
        return once(function () {
            return rand(1, 10000);
        });
    }
};

No matter how many times you run $myClass->getNumber() you'll always get the same number.

The once function will only run once per combination of argument values the containing method receives.

class MyClass
{
    /**
     * It also works in static context!
     */
    public static function getNumberForLetter($letter)
    {
        return once(function () use ($letter) {
            return $letter . rand(1, 10000000);
        });
    }
}

So calling MyClass::getNumberForLetter('A') will always return the same result, but calling MyClass::getNumberForLetter('B') will return something else.

#Flushing the cache

To flush the entire cache you can call:

Spatie\Once\Cache::getInstance()->flush();

#Disabling the cache

In your tests you probably don't want to cache values. To disable the cache you can call:

Spatie\Once\Cache::getInstance()->disable();

You can re-enable the cache with

Spatie\Once\Cache::getInstance()->enable();

#Octane compatibility

Warning

This behaviour is in beta and needs to be tested by the community. You can find this topic in discussion #79.

In order to have once working properly in an Octane environment, Cache::getInstance()->flush() must be called when OperationTerminated event is triggered. You can configure it in config/octane.php file:

// config/octane.php

OperationTerminated::class => [
    FlushTemporaryContainerInstances::class,
    // DisconnectFromDatabases::class,
    // CollectGarbage::class,

    FlushSpatieOnce::class, // we should create this class we have added here
],

And create the FlushSpatieOnce:class:

// app/Listeners/FlushSpatieOnce.php

use Spatie\Once\Cache;

class FlushSpatieOnce
{
    public function handle($event)
    {
        Cache::getInstance()->flush();
    }
}

#Under the hood

The once function will execute the given callable and save the result in the $values property of Spatie\Once\Cache. This class is a singleton. When we detect that once has already run before, we're just going to return the value stored inside the $values weakmap instead of executing the callable again.

The first thing it does is calling debug_backtrace. We'll use the output to determine in which function and class once is called and to get access to the object that function is running in. Yeah, we're already in voodoo-land. The output of the debug_backtrace is passed to a new instance of Backtrace. That class is just a simple wrapper, so we can work more easily with the backtrace.

$trace = debug_backtrace(
    DEBUG_BACKTRACE_PROVIDE_OBJECT, 2
)[1];

$backtrace = new Backtrace($trace);

$object = $backtrace->getObject();

Next, we calculate a hash of the backtrace. This hash will be unique per function once was called in and the values of the arguments that function receives.

$hash = $backtrace->getHash();

Finally, we will check if there's already a value stored for the given hash. If not, then execute the given $callback and store the result in the weakmap of Spatie\Once\Cache. In the other case, we just return the value from that cache (the $callback isn't executed).

public function has(object $object, string $backtraceHash): bool
{
    if (! isset($this->values[$object])) {

        return false;
    }

    return array_key_exists($backtraceHash, $this->values[$object]);
}

#Changelog

Please see CHANGELOG for more information what has changed recently.

#Testing

composer test

#Contributing

Please see CONTRIBUTING for details.

#Security

If you've found a bug regarding security please mail security@spatie.be instead of using the issue tracker.

#Credits

• Freek Van der Herten
• All Contributors

And a special thanks to Caneco for the logo ✨

Credit for the idea of the once function goes to Taylor Otwell. The code for this package is based upon the code he was kind enough to share with us.

#License

The MIT License (MIT). Please see License File for more information.