From the About section on GitHub of ramsey/uuid package:

A PHP library for generating universally unique identifiers (UUIDs).

First thing we notice that its not a Laravel package, instead a PHP library and it can be used in any PHP project. Secondly, universally unique identifiers (UUIDs), let's talk a bit about what are UUIDs.

What is a UUID?

UUID stands for Universally Unique Identifier. When it says Universally, it truly means Universally.

When you generate a UUID, its uniqueness can be guaranteed across space and time.

A UUID is 128 bits long and is usually represented as a hexadecimal string split into five groups with dashes, like below:

998fd066-c786-4064-9c98-e378e450cd4a

We can use these unique values and assign them to our database records and later identify the records by these hexadecimal strings.

UUIDs in Laravel

Laravel framework is famous for best Developer Experience (DX), therefore, Laravel makes it a cinch to work with UUIDs. If you open the tinker in Laravel project and write below code snippet:

(string) Str::uuid();

You'll get an output like below:

"220b94fc-04f9-48eb-a14a-ba868ff43919"

It's just that simple to create UUIDs in Laravel. Now let's take a look at how it works and where ramsey/uuid package comes into play.

Code Dive

If we dive into the definition of Str::uuid() method, we see the following:

<?php

namespace Illuminate\Support;

use Ramsey\Uuid\Uuid;

class Str
{

    /**
     * The callback that should be used to generate UUIDs.
     *
     * @var callable
     */
    protected static $uuidFactory;


    /**
     * Generate a UUID (version 4).
     *
     * @return \Ramsey\Uuid\UuidInterface
     */
    public static function uuid()
    {
        return static::$uuidFactory
                    ? call_user_func(static::$uuidFactory)
                    : Uuid::uuid4();
    }

    /**
     * Set the callable that will be used to generate UUIDs.
     *
     * @param  callable|null  $factory
     * @return void
     */
    public static function createUuidsUsing(callable $factory = null)
    {
        static::$uuidFactory = $factory;
    }

}

If we first call createUuidsUsing() method and provide a callback that will create UUIDs, then uuid() method will execute that callback to generate a UUID. But if that's not the case, it will use Uuid::uuid4() from ramsey/uuid to generate the UUID for us. This is how Laravel is able to generate UUIDs by leveraging ramsey/uuid package.

You might be wondering about why this method is named as uuid4() ? What does 4 mean here?

There are five versions of UUIDs. Each version has different algorithm to generate it. Read more about all versions in ramsey/uuid package docs.

UUIDs in Laravel migrations

Laravel provides a handy method on Illuminate\Database\Schema\Blueprint class named uuid to specify in migrations that this column will be used to store a UUID.

$table->uuid('id');

You might wonder if there's a column type in database which stores UUIDs, but that's not the case. If we look inside the Illuminate\Database\Schema\Grammars\MySqlGrammar class and find the typeUuid() method, we can see the following:

    /**
     * Create the column definition for a uuid type.
     *
     * @param  \Illuminate\Support\Fluent  $column
     * @return string
     */
    protected function typeUuid(Fluent $column)
    {
        return 'char(36)';
    }

Which means that $table->uuid() will be translated to a column wich char data type and its length would be 36 characters, always.

Laravel does not generate UUIDs automatically for uuid columns. Developer must provide the logic to generate UUIDs when inserting records in the database.

Interesting facts about ramsey/uuid in Laravel context

• This package was first required on 08 Aug, 2016 by Taylor Otwell when he worked on channel specific notifications. UUIDs were used to identify the database notifications.
• Link to commit by Taylor Otwell.
• Version ~3.0 was used initially in Laravel v5.3
• UUID helper methods were introduced in Laravel v5.6.
• Link to commit by Taylor Otwell which added the helper methods

I hope you enjoyed this post. Next, we will see why Laravel requires swiftmailer/swiftmailer package. You can follow me on Twitter or join my newsletter for more content.