« back — written by Brent on July 29, 2021

The evolution of a PHP object throughout the years

This is just a fun little post I wrote because I wanted to visualise how my data transfer objects have evolved over the years.

# August 2014: PHP 5.6

Let's start with PHP 5.6, this is what most people without modern-day PHP knowledge probably think PHP code still looks like. I'll just give you the code, and I'll mention what changes in future versions.

class BlogData
{
    /** @var string */
    private $title;
    
    /** @var State */
    private $state;
    
    /** @var \DateTimeImmutable|null */
    private $publishedAt;
   
   /**
    * @param string $title 
    * @param State $state 
    * @param \DateTimeImmutable|null $publishedAt 
    */
    public function __construct(
        $title,
        $state,
        $publishedAt = null
    ) {
        $this->title = $title;
        $this->state = $state;
        $this->publishedAt = $publishedAt;
    }
    
    /**
     * @return string 
     */
    public function getTitle()
    {
        return $this->title;    
    }
    
    /**
     * @return State 
     */
    public function getState() 
    {
        return $this->state;    
    }
    
    /**
     * @return \DateTimeImmutable|null 
     */
    public function getPublishedAt() 
    {
        return $this->publishedAt;    
    }
}

# December 2015: PHP 7.0

PHP 7.0 introduced some major new syntax features: scalar types and return types being the most notable here. Nullable types aren't a thing yet, so we still need to use doc block types for our nullable $publishedAt:

class BlogData
{
    /** @var string */
    private $title;
    
    /** @var State */
    private $state;
    
    /** @var \DateTimeImmutable|null */
    private $publishedAt;
   
   /**
    * @param \DateTimeImmutable|null $publishedAt 
    */
    public function __construct(
        string $title,
        State $state,
        $publishedAt = null
    ) {
        $this->title = $title;
        $this->state = $state;
        $this->publishedAt = $publishedAt;
    }
    
    public function getTitle(): string
    {
        return $this->title;    
    }
    
    public function getState(): State 
    {
        return $this->state;    
    }
    
    /**
     * @return \DateTimeImmutable|null 
     */
    public function getPublishedAt() 
    {
        return $this->publishedAt;    
    }
}

# December 2016: PHP 7.1

With PHP 7.1 finally came nullable types, so we could remove some more doc blocks:

class BlogData
{
    /** @var string */
    private $title;
    
    /** @var State */
    private $state;
    
    /** @var \DateTimeImmutable|null */
    private $publishedAt;
   
    public function __construct(
        string $title,
        State $state,
        ?DateTimeImmutable $publishedAt = null
    ) {
        $this->title = $title;
        $this->state = $state;
        $this->publishedAt = $publishedAt;
    }
    
    public function getTitle(): string
    {
        return $this->title;    
    }
    
    public function getState(): State 
    {
        return $this->state;    
    }
    
    public function getPublishedAt(): ?DateTimeImmutable
    {
        return $this->publishedAt;    
    }
}

# November 2017: PHP 7.2

While there were some exciting features in 7.2 like parameter type widening and the object type, there's nothing we could do to clean up our specific DTO in this release.

# December 2018: PHP 7.3

The same goes for PHP 7.3, nothing to see here.

# November 2019: PHP 7.4

PHP 7.4 is a different story though! There now are typed properties — finally!

class BlogData
{
    private string $title;
    
    private State $state;
    
    private ?DateTimeImmutable $publishedAt;
   
    public function __construct(
        string $title,
        State $state,
        ?DateTimeImmutable $publishedAt = null
    ) {
        $this->title = $title;
        $this->state = $state;
        $this->publishedAt = $publishedAt;
    }
    
    public function getTitle(): string
    {
        return $this->title;    
    }
    
    public function getState(): State 
    {
        return $this->state;    
    }
    
    public function getPublishedAt(): ?DateTimeImmutable
    {
        return $this->publishedAt;    
    }
}

# November 2020: PHP 8.0

Another game changer: PHP 8 adds promoted properties!

class BlogData
{
    public function __construct(
        private string $title,
        private State $state,
        private ?DateTimeImmutable $publishedAt = null
    ) {}
    
    public function getTitle(): string
    {
        return $this->title;    
    }
    
    public function getState(): State 
    {
        return $this->state;    
    }
    
    public function getPublishedAt(): ?DateTimeImmutable
    {
        return $this->publishedAt;    
    }
}

# November 2021: PHP 8.1

And finally, we arrive at PHP 8.1 — not released yet. Readonly properties are a thing, and allow us to write our DTO like so:

class BlogData
{
    public function __construct(
        public readonly string $title,
        public readonly State $state,
        public readonly ?DateTimeImmutable $publishedAt = null
    ) {}
}

That's quite the difference, don't you think?

It's interesting to see how the language has evolved over the course of almost a decade. If you had proposed the 8.1 syntax 10 years ago, you'd probably be called a madman. The same is true today, and I'm sure we'll look back at this point, ten years from now and wonder "how did we ever put up with that?".