Ex1a.php

class User
{
    ...
    protected $portfolioUrl;
    
    public function setPortfolioUrl(string $url)
    {
        if (false === filter_var($url, FILTER_VALIDATE_URL)) {
        	throw new InvalidURL($url);
        }
        $this->portfolioUrl = $url;
    }
    
    public function getPortfolioUrl():string
    {
    	  return $this->portfolioUrl;
    }
    ...
}

Ex1b.php

class User
{
    ...
    protected $portfolioUrl;
    
    public function setPortfolioUrl(Url $url)
    {
        $this->portfolioUrl = $url;
    }
    
    public function getPortfolioUrl():Url
    {
    	  return $this->portfolioUrl;
    }
    ...
}

class Url
{
    protected $url;
    
    public function setUrl(string $url)
    {
        if (false === filter_var($url, FILTER_VALIDATE_URL)) {
        	throw new InvalidURL($url);
        }
        $this->url = $url;
    }
    
    public function getUrl():string
    {
    	  return $this->url;
    }
    ...
}

Ex2a.php

class User
{
    ...
    const SINGLE = ‘S’;
    const IN_RELATIONSHIP = ‘R’;
    
    protected $relationship;
    
    public function setRelationship(string $relationship)
    {
        $this->relationship = $relationship;
    }
    
    public function getRelationship():string
    {
    	  return $this->relationship;
    }
    ...
}

Ex2b.php

class User
{
    ...
    protected $relationship;
    
    public function setRelationship(Relationship $relationship)
    {
        $this->relationship = $relationship;
    }
    
    public function getRelationship():Relationship
    {
    	  return $this->relationship;
    }
    ...
}

class Relationship
{
    private $relationshipCode;

    private function __construct($relationshipCode)
    {
        $this->relationshipCode = $relationshipCode;
    }

    public function getRelationshipCode()
    {
        return $this->relationshipCode;
    }

    public static function single():Relationship
    {
        return new self('S');
    }

    public static function inRelationship():Relationship
    {
        return new self('R');
    }
}

Ex3a.php

class Offer
{
    ...
    const DRAFT = 1;
    const PUBLISHED = 2;
    const CANCELED = 3;
    ...
    
    protected $status;
    
    public function setStatus(int $status)
    {
        $this->status = $status;
    }
    
    public function getStatus():int
    {
    	  return $this->status;
    }
    ...
}

Ex3b.php

class Offer
{
    ...
    const DRAFT = 1;
    const PUBLISHED = 2;
    Const CANCELLED = 3;
    ...

    protected $status;
    
    public function setStatus(OfferStatus $status)
    {
        $this-status = $status;
    }
    
    public function getStatus():OfferStatus
    {
    	  return $this->status;
    }
    ...
}

abstract class OfferStatus
{
    public abstract function getCode();
}

class DraftOffer extends OfferStatus
{
    public function getCode()
    {
        return Offer::DRAFT;
    }
}

class PublishedOffer extends OfferStatus
{
    public function getCode()
    {
        return Offer::PUBLISHED;
    }
}

class CancelledOffer extends OfferStatus
{
    public function getCode()
    {
        return Offer::CANCELLED;
    }
}

Ex4a.php

$todo = [];
$todo[0][‘description’] = ‘feed cat’;
$todo[0][‘done’] = true;
...

Ex4b.php

class Todo
{
    protected $description;
    protected $done;
    
    public function __construct(string $description, bool $done)
    {
        $this->description = $description;
        $this->done = $done;
    }

    public function setDone(bool $done)
    {
        $this->done = $done;
    }
    ...
}