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PHP 8.4 akan dikeluarkan pada November 2024 dan akan membawakan ciri baharu yang menarik: pengait harta benda.

Dalam artikel ini, kami akan melihat apakah cangkuk hartanah dan cara anda boleh menggunakannya dalam projek PHP 8.4 anda.

Sebagai nota sampingan, anda mungkin juga berminat untuk menyemak artikel saya yang lain yang menunjukkan kepada anda fungsi tatasusunan baharu yang ditambah dalam PHP 8.4.

Apakah itu PHP Property Hooks?

Cakuk harta membolehkan anda menentukan logik pengambil dan penetap tersuai untuk sifat kelas tanpa perlu menulis kaedah pengambil dan penetap yang berasingan. Ini bermakna anda boleh mentakrifkan logik secara langsung dalam pengisytiharan harta supaya anda boleh mengakses terus harta (seperti $user->firstName) tanpa perlu ingat untuk memanggil kaedah (seperti $user->getFirstName() dan $user- >setFirstName()).

Anda boleh menyemak RFC untuk ciri ini di https://wiki.php.net/rfc/property-hooks

Jika anda seorang pembangun Laravel, semasa anda membaca artikel ini, anda mungkin perasan bahawa cangkuk kelihatan sangat serupa dengan pengakses dan mutator dalam model Laravel.

Saya sangat menyukai rupa ciri cangkuk hartanah dan saya membayangkan ia adalah sesuatu yang saya akan gunakan dalam projek saya apabila PHP 8.4 dikeluarkan.

Untuk memahami cara cangkuk hartanah berfungsi, mari kita lihat beberapa contoh penggunaan.

Cangkuk "dapatkan".

Anda boleh menentukan cangkuk get yang akan dipanggil apabila anda cuba mengakses harta benda.

Sebagai contoh, bayangkan anda mempunyai kelas Pengguna ringkas yang menerima nama pertama dan Nama akhir dalam pembina. Anda mungkin mahu mentakrifkan sifat Nama penuh yang menggabungkan nama pertama dan nama akhir bersama-sama. Untuk melakukan ini, anda boleh menentukan cangkuk get untuk sifat nama penuh:

readonly class User
{
    public string $fullName {
        get {
            return $this->firstName.' '.$this->lastName;
        }
    }

    public function __construct(
        public readonly string $firstName,
        public readonly string $lastName
    ) {
        //
    }
}

$user = new User(firstName: 'ash', lastName: 'allen');

echo $user->firstName; // ash
echo $user->lastName; // allen
echo $user->fullName; // ash allen

Dalam contoh di atas, kita dapat melihat bahawa kita telah menentukan get hook untuk sifat nama penuh yang mengembalikan nilai yang dikira dengan menggabungkan sifat firstName dan lastName bersama-sama. Kita boleh membersihkannya sedikit lagi dengan menggunakan sintaks yang serupa dengan fungsi anak panah juga:

readonly class User
{
    public string $fullName {
        get =>  $this->firstName.' '.$this->lastName;
    }

    public function __construct(
        public readonly string $firstName,
        public readonly string $lastName,
    ) {
        //
    }
}

$user = new User(firstName: 'ash', lastName: 'allen');

echo $user->firstName; // ash
echo $user->lastName; // allen
echo $user->fullName; // ash allen

Jenis Keserasian

Perlu ambil perhatian bahawa nilai yang dikembalikan daripada pengambil mesti serasi dengan jenis harta benda.

Jika jenis yang ketat tidak didayakan, nilai akan ditaip-dijuggle ke jenis sifat. Sebagai contoh, jika anda mengembalikan integer daripada sifat yang diisytiharkan sebagai rentetan, integer akan ditukar kepada rentetan:

declare(strict_types=1);

class User
{
    public string $fullName {
        get {
            return 123;
        }
    }

    public function __construct(
        public readonly string $firstName,
        public readonly string $lastName,
    ) {
        //
    }
}

$user = new User(firstName: 'ash', lastName: 'allen');

echo $user->fullName; // "123"

Dalam contoh di atas, walaupun kami telah menentukan 123 sebagai integer untuk dikembalikan, "123" dikembalikan sebagai rentetan kerana sifat itu ialah rentetan.

Kami boleh menambah declare(strict_types=1); ke bahagian atas kod seperti itu untuk membolehkan semakan jenis yang ketat:

declare(strict_types=1);

class User
{
    public string $fullName {
        get {
            return 123;
        }
    }

    public function __construct(
        public readonly string $firstName,
        public readonly string $lastName,
    ) {
        //
    }
}

Sekarang ini akan menyebabkan ralat dilemparkan kerana nilai pulangan ialah integer, tetapi sifatnya ialah rentetan:

Fatal error: Uncaught TypeError: User::$fullName::get(): Return value must be of type string, int returned

Cangkuk "set".

Cangkok harta PHP 8.4 juga membolehkan anda menentukan cangkuk set. Ini dipanggil apabila anda cuba menetapkan sifat.

Anda boleh memilih antara dua sintaks berasingan untuk cangkuk set:

• Mentakrifkan secara eksplisit nilai untuk ditetapkan pada harta itu
• Menggunakan fungsi anak panah untuk mengembalikan nilai untuk ditetapkan pada harta

Mari kita lihat kedua-dua pendekatan ini. Kami akan bayangkan kami mahu huruf besar huruf pertama nama pertama dan nama keluarga apabila ia ditetapkan pada kelas Pengguna:

declare(strict_types=1);

class User
{   
    public string $firstName {
        // Explicitly set the property value
        set(string $name) {
            $this->firstName = ucfirst($name);
        }
    }

    public string $lastName {
        // Use an arrow function and return the value
        // you want to set on the property 
        set(string $name) => ucfirst($name);
    }

    public function __construct(
        string $firstName,
        string $lastName
    ) {
        $this->firstName = $firstName;
        $this->lastName = $lastName;
    }
}

$user = new User(firstName: 'ash', lastName: 'allen');

echo $user->firstName; // Ash
echo $user->lastName; // Allen

Seperti yang dapat kita lihat dalam contoh di atas, kami telah mentakrifkan cangkuk set untuk sifat firstName yang menggunakan huruf besar pada huruf pertama nama sebelum menetapkannya pada harta tersebut. Kami juga telah menentukan cangkuk set untuk sifat lastName yang menggunakan fungsi anak panah untuk mengembalikan nilai untuk ditetapkan pada harta tersebut.

Jenis Keserasian

Jika harta mempunyai pengisytiharan jenis, maka cangkuk setnya mesti mempunyai set jenis yang serasi juga. Contoh berikut akan mengembalikan ralat kerana cangkuk set untuk firstName tidak mempunyai pengisytiharan jenis, tetapi harta itu sendiri mempunyai pengisytiharan jenis rentetan:

class User
{   
    public string $firstName {
        set($name) => ucfirst($name);
    }

    public string $lastName {
        set(string $name) => ucfirst($name);
    }

    public function __construct(
        string $firstName,
        string $lastName
    ) {
        $this->firstName = $firstName;
        $this->lastName = $lastName;
    }
}

Percubaan untuk menjalankan kod di atas akan menyebabkan ralat berikut dilemparkan:

Fatal error: Type of parameter $name of hook User::$firstName::set must be compatible with property type

Menggunakan "get" dan "set" Hooks Together

Anda tidak terhad kepada menggunakan cangkuk get dan set secara berasingan. Anda boleh menggunakannya bersama-sama dalam harta yang sama.

Mari kita ambil contoh mudah. Kami akan bayangkan kami mempunyai sifat Nama penuh pada kelas Pengguna kami. Apabila kami menetapkan harta itu, kami akan membahagikan nama penuh kepada nama pertama dan nama keluarga. Saya tahu ini adalah pendekatan yang naif dan terdapat banyak penyelesaian yang lebih baik, tetapi ia semata-mata untuk contoh untuk menyerlahkan sifat ketagih.

Kod mungkin kelihatan seperti itu:

declare(strict_types=1);

class User
{
    public string $fullName {
        // Dynamically build up the full name from
        // the first and last name
        get => $this->firstName.' '.$this->lastName;

        // Split the full name into first and last name and
        // then set them on their respective properties
        set(string $name) {
            $splitName = explode(' ', $name);
            $this->firstName = $splitName[0];
            $this->lastName = $splitName[1];
        }
    }

    public string $firstName {
        set(string $name) => $this->firstName = ucfirst($name);
    }

    public string $lastName {
        set(string $name) => $this->lastName = ucfirst($name);
    }

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

$user = new User(fullName: 'ash allen');

echo $user->firstName; // Ash
echo $user->lastName; // Allen
echo $user->fullName; // Ash Allen

In the code above, we've defined a fullName property that has both a get and set hook. The get hook returns the full name by concatenating the first and last name together. The set hook splits the full name into the first and last name and sets them on their respective properties.

You may have also noticed that we're not setting a value on the fullName property itself. Instead, if we need to read the value of the fullName property, the get hook will be called to build up the full name from the first and last name properties. I've done this to highlight that you can have a property that doesn't have a value set directly on it, but instead, the value is calculated from other properties.

Using Property Hooks on Promoted Properties

A cool feature of property hooks is that you can also use them with constructor promoted properties.

Let's check out an example of a class that isn't using promoted properties and then look at what it might look like using promoted properties.

Our User class might look like so:

readonly class User
{
    public string $fullName {
        get => $this->firstName.' '.$this->lastName;
    }

    public string $firstName {
        set(string $name) => ucfirst($name);
    } 

    public string $lastName {
        set(string $name) => ucfirst($name);
    }

    public function __construct(
        string $firstName,
        string $lastName,
    ) {
        $this->firstName = $firstName;
        $this->lastName = $lastName;
    }
}

We could promote the firstName and lastName properties into the constructor and define their set logic directly on the property:

readonly class User
{
    public string $fullName {
        get => $this->firstName.' '.$this->lastName;
    }

    public function __construct(
        public string $firstName {
            set (string $name) => ucfirst($name);
        }, 
        public string $lastName {
            set (string $name) => ucfirst($name);
        }
    ) {
        //
    }
}  

Write-only Hooked Properties

If you define a hooked property with a setter that doesn't actually set a value on the property, then the property will be write-only. This means you can't read the value of the property, you can only set it.

Let's take our User class from the previous example and modify the fullName property to be write-only by removing the get hook:

declare(strict_types=1);

class User
{
    public string $fullName {
        // Define a setter that doesn't set a value
        // on the "fullName" property. This will
        // make it a write-only property.
        set(string $name) {
            $splitName = explode(' ', $name);
            $this->firstName = $splitName[0];
            $this->lastName = $splitName[1];
        }
    }

    public string $firstName {
        set(string $name) => $this->firstName = ucfirst($name);
    }

    public string $lastName {
        set(string $name) => $this->lastName = ucfirst($name);
    }

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

$user = new User('ash allen');

echo $user->fullName; // Will trigger an error!

If we were to run the code above, we'd see the following error being thrown when attempting to access the fullName property:

Fatal error: Uncaught Error: Property User::$fullName is write-only

Read-only Hooked Properties

Similarly, a property can be read-only.

For example, imagine we only ever want the fullName property to be generated from the firstName and lastName properties. We don't want to allow the fullName property to be set directly. We can achieve this by removing the set hook from the fullName property:

class User
{
    public string $fullName {
        get {
            return $this->firstName.' '.$this->lastName;
        }
    }

    public function __construct(
        public readonly string $firstName,
        public readonly string $lastName,
    ) {
        $this->fullName = 'Invalid'; // Will trigger an error!
    }
}

If we were to try and run the code above, the following error would be thrown because we're trying to set the fullName property directly:

Uncaught Error: Property User::$fullName is read-only

Using the "readonly" keyword

You can still make our PHP classes readonly even if they have hooked properties. For example, we may want to make the User class readonly:

readonly class User
{   
    public string $firstName {
        set(string $name) => ucfirst($name);
    }

    public string $lastName {
        set(string $name) => ucfirst($name);
    }

    public function __construct(
        string $firstName,
        string $lastName,
    ) {
        $this->firstName = $firstName;
        $this->lastName = $lastName;
    }
}

However, a hooked property cannot use the readonly keyword directly. For example, this class would be invalid:

class User
{
    public readonly string $fullName {
        get => $this->firstName.' '.$this->lastName;
    }

    public function __construct(
        string $firstName,
        string $lastName,
    ) {
        $this->firstName = $firstName;
        $this->lastName = $lastName;
    }
}

The above code would throw the following error:

Fatal error: Hooked properties cannot be readonly

The "PROPERTY" Magic Constant

In PHP 8.4, a new magic constant called __PROPERTY__ has been introduced. This constant can be used to reference the property name within the property hook.

Let's take a look at an example:

class User
{
    // ...

    public string $lastName {
        set(string $name) {
            echo __PROPERTY__; // lastName
            $this->{__PROPERTY__} = ucfirst($name); // Will trigger an error!
        }
    }

    public function __construct(
        string $firstName,
        string $lastName,
    ) {
        $this->firstName = $firstName;
        $this->lastName = $lastName;
    }
}

In the code above, we can see that using __PROPERTY__ inside the lastName property's setter will output the property name lastName. However, it's also worth noting that trying to use this constant in an attempt to set the property value will trigger an error:

Fatal error: Uncaught Error: Must not write to virtual property User::$lastName

There's a handy use case example for the __PROPERTY__ magic constant that you can check out on GitHub: https://github.com/Crell/php-rfcs/blob/master/property-hooks/examples.md.

Hooked Properties in Interfaces

PHP 8.4 also allows you to define publicly accessible hooked properties in interfaces. This can be useful if you want to enforce that a class implements certain properties with hooks.

Let's take a look at an example interface with hooked properties declared:

interface Nameable
{
    // Expects a public gettable 'fullName' property
    public string $fullName { get; }

    // Expects a public gettable 'firstName' property
    public string $firstName { get; }

    // Expects a public settable 'lastName' property
    public string $lastName { set; }
}

In the interface above, we're defining that any classes implementing the Nameable interface must have:

• A fullName property that is at least publicly gettable. This can be achieved by defining a get hook or not defining a hook at all.
• A firstName property that is at least publicly gettable.
• A lastName property that is at least publicly settable. This can be achieved by defining a property which has a set hook or not defining a hook at all. But if the class is read-only then the property must have a set hook.

This class that implements the Nameable interface would be valid:

class User implements Nameable
{
    public string $fullName {
        get => $this->firstName.' '.$this->lastName;
    }

    public string $firstName {
        set(string $name) => ucfirst($name);
    }

    public string $lastName;

    public function __construct(
        string $firstName,
        string $lastName,
    ) {
        $this->firstName = $firstName;
        $this->lastName = $lastName;
    }
}

The class above would be valid because the fullName property has a get hook to match the interface definition. The firstName property only has a set hook, but is still publicly accessible so it satisfies the criteria. The lastName property doesn't have a get hook, but it is publicly settable so it satisfies the criteria.

Let's update our User class to enforce a get and set hook for the fullName property:

interface Nameable
{
    public string $fullName { get; set; }

    public string $firstName { get; }

    public string $lastName { set; }
}

Our User class would no longer satisfy the criteria for the fullName property because it doesn't have a set hook defined. It would cause the following error to be thrown:

Fatal error: Class User contains 1 abstract methods and must therefore be declared abstract or implement the remaining methods (Nameable::$fullName::set)

Hooked Properties in Abstract Classes

Similar to interfaces, you can also define hooked properties in abstract classes. This can be useful if you want to provide a base class that defines hooked properties that child classes must implement. You can also define the hooks in the abstract class and have them be overridden in the child classes.

For example, let's make a Model abstract class that defines a name property that must be implemented by child classes:

abstract class Model
{
    abstract public string $fullName {
        get => $this->firstName.' '.$this->lastName;
        set;
    }

    abstract public string $firstName { get; }

    abstract public string $lastName { set; }
}

In the abstract class above, we're defining that any classes that extend the Model class must have:

• A fullName property that is at least publicly gettable and settable. This can be achieved by defining a get and set hook or not defining a hook at all. We've also defined the get hook for the fullName property in the abstract class so we don't need to define it in the child classes, but it can be overridden if needed.
• A firstName property that is at least publicly gettable. This can be achieved by defining a get hook or not defining a hook at all.
• A lastName property that is at least publicly settable. This can be achieved by defining a property which has a set hook or not defining a hook at all. But if the class is read-only then the property must have a set hook.

We could then create a User class that extends the Model class:

class User extends Model
{
    public string $fullName;

    public string $firstName {
        set(string $name) => ucfirst($name);
    }

    public string $lastName;

    public function __construct(
        string $firstName,
        string $lastName,
    ) {
        $this->firstName = $firstName;
        $this->lastName = $lastName;
    }
}

Conclusion

Hopefully, this article should have given you an insight into how PHP 8.4 property hooks work and how you might be able to use them in your PHP projects.

I wouldn't worry too much if this feature seems a little confusing at first. When I first saw it, I was a little confused too (especially with how they work with interfaces and abstract classes). But once you start tinkering with them, you'll soon get the hang of it.

I'm excited to see how this feature will be used in the wild and I'm looking forward to using it in my projects when PHP 8.4 is released.

If you enjoyed reading this post, you might be interested in checking out my 220+ page ebook "Battle Ready Laravel" which covers similar topics in more depth.

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