PHP - Can't Unserialize Objects?

Is this a mistake in the documentation?  I am running PHP7.4 and get warning: unserialize() expects parameter 2 to be array, bool given.

Either an array of class names which should be accepted, false to accept no classes, or true to accept all classes. If this option is defined and unserialize() encounters an object of a class that isn't to be accepted, then the object will be instantiated as __PHP_Incomplete_Class instead. Omitting this option is the same as defining it as true: PHP will attempt to instantiate objects of any class.

I have the following three tables (and also delta_point and hist_point which are purposely left out and just mentioned for context).  Before going down the Doctrine ORM long curvy road, aggrType was just used to restrict possible values so that I didn't need to use MySQL's ENUM, but now I am thinking there may be value to making it an entity and include some methods (and a second reason because I still can't figure out how to make Doctrine create a FK constraint yet not populate the parent entity with a AggrType object).

point
-id (int PK)
-data
-dType /* descriminator.  Options are AggregatePoint, DeltaPoint, and HistoricPoint */

aggr_point
-id (int PK, FK to point)
-aggrType (char FK to aggrType)
-data

aggrType
-type (char PK) /* there are about five types */

I have a service to create a new point based on the provided desired type and user data.  I don't like the switch statement to determine which type of point to create, but don't know a better way.  Also my entity is responsible to provide the appropriate validation rules for the given point type which might not be considered proper but it seems to work for me.  Any constructive criticism is welcomed.

<?php
namespace NotionCommotion\PointMapper\Api\Point;
use NotionCommotion\PointMapper\Domain\Entity\Point;
class PointService
{
    public function create(string $type, array $params):integer {
        $class=[
            'aggr'=>'AggregatePoint',
            'delta'=>'DeltaPoint',
            'hist'=>'HistoricPoint',
        ][$type];
        //$class='Point\\'.$class;  //This doesn't seem to be possible and I needed to use the fully qualifed name without the short cut used namespace.
        $class='\\Greenbean\Datalogger\Domain\Entity\Point\\'.$class;
        $point=new $class();
        $validator=$this->getValidator($point);
        $params=$validator->sanitize($params);
        $validator->validate($params);
        $point->setAccount($this->account);
        $point->populate($params, $this->em); //Will be addressed later
        $this->em->persist($point);
        $this->em->flush();
        $point->setIdPublic($this->em->getRepository(Point\Point::class)->getPublicId($point->getId()));
        return $point->getIdPublic();
    }
}

Now, this is the part I am struggling with the most.  I only have one service to create any type of point, so I do wish to put a bunch of if/thens in it and instead move logic to the individual point type being created.  The AggrPoint in question requires a sub-point and I don't think it is appropriate to inject the entity manager into a point entity and as an alternative solution find an existing point which is associated with the account which resides in the new AggrPoint.  Maybe not appropriate, but it works.  This type of point also has a sub-object AggrType as discussed at the very beginning of this post, so I first attempt to create a new one from scratch, but that doesn't work and I need to set $aggrType with an existing one.  As an alternative, I passed the entity the entity manager, but as stated I think this is a bad idea.

Any recommendations where to go from here?  Thank you

namespace NotionCommotion\PointMapper\Domain\Entity\Point;
class AggregatePoint extends Point
{
    public function populate(array $params, \Doctrine\ORM\EntityManager $em):\NotionCommotion\PointMapper\Domain\Entity\Entity{
        $criteria = \Doctrine\Common\Collections\Criteria::create()
        ->where(\Doctrine\Common\Collections\Criteria::expr()->eq("id_public", $params['pointId']));
        if(!$subpoint = $this->getAccount()->getPoints()->matching($criteria)->current()){
            throw new \Exception("Invalid subpoint ID $params[pointId]");
        }
        $this->setSubpoint($subpoint);

        //This won't work since I must use an existing AggregateType and not create a new one
        $aggrType=new AggregateType();
        $aggrType->setType($params['aggrType']);

        //This just seems wrong and I shouldn't be passing the entity manager to an entity
        $aggrType=$em->getRepository(AggregateType::class)->findOneBy(['type'=>$params['aggrType']]);

        $this->setAggregateType($aggrType);

        unset($params['pointId'], $params['aggrType']);
        // parent::populate($params) not shown, but it basically calles appropriate setters based on the property name
        return parent::populate($params);
    }

    public function getValidatorRules():array
    {
        return $this->filesToArr(['/point/base.json', '/point/aggr.json']);
    }

}

Hi I am new to PHP and I need to create an array and add both books to the array and than loop through the array this is where I am having trouble if the price of a book is less than $20.00 output the book’s name and price if the book’s title comes after the letter R in the alphabet output the book’s title.

I am getting these error:

Notice: Trying to get property 'price' of non-object in C:\xampp\htdocs\PHP objects\books.php on line 45

Notice: Trying to get property 'title' of non-object in C:\xampp\htdocs\PHP objects\books.php on line 49

Notice: Trying to get property 'price' of non-object in C:\xampp\htdocs\PHP objects\books.php on line 50

Fatal error: Uncaught Error: Call to a member function get_first_char() on string in C:\xampp\htdocs\PHP objects\books.php:52 Stack trace: #0 {main} thrown in C:\xampp\htdocs\PHP objects\books.php on line 52

My code is:

<?php
class Book {
  // Properties
  public $price;
  public $title;
  public function get_first_char() {
    $titleArray = str_split($this->title);
    return reset($titleArray);
}

  // Methods
  function set_price($price) {
    $this->price = $price;
  }
  function get_price() {
    return $this->price;
  }
  function set_title($title) {
    $this->title = $title;
  }
  function get_title() {
    return $this->title;
  }
  
}

$first_book = new Book();
$first_book->set_price('$13.95');
$first_book->set_title('Moby Dick');
echo "Price: " . $first_book->get_price();
echo "<br>";
echo "Title: " .  $first_book->get_title();
echo "<br>";
$second_book = new Book();
$second_book->set_price('$23.99');
$second_book->set_title('Wuthering Heights');
echo "Price: " . $second_book->get_price();
echo "<br>";
echo "Title: " .  $second_book->get_title();
echo "<br>";
$book = array("Moby Dick", "Wuthering Heights");
echo "Book Titles: " . $book[0] . ", "  . " and " . $book[1] . ".";

foreach ($book as $bookItem) {
    $price = $bookItem->price;
    // Right now $price is a string ('$xx.xx'), we need it to be numeric
    $price = (float) substr($price, 1);
    if ($price < 20) {
        echo $bookItem->title;
        echo $bookItem->price;
    }
    if (ord(strtoupper($bookItem->get_first_char())) > ord('R')) {
        echo $bookItem->title;
    }
}
 ?>

Any help will be very much appreciated

Thank you

I know it is often frivolous, but sometimes I can't help trying to optimize things, and use the following two methods to create either an object injected with a string or one of a set of objects.  For both cases, the class has no setters so there is no chance that the object will later be changed.  I first stated doing this in continuously running server applications which I believe makes sense, however, it has leaked over to standard HTTP requests.

Please commit good or bad on this approach. Thanks

    public static function create(string $unit):self
    {
        static $stack=[];
        if(!isset($stack[$unit])) {
            $stack[$unit] = new self($unit);
        }
        return $stack[$unit];
    }

    public static function create(string $class):FunctionInterface
    {
        static $stack=[];
        if(!isset($stack[$class])) {
            $stack[$class] = new $class;
        }
        return $stack[$class];
    }

I found it helpful to configure all my objects in one or several bootstrap scripts.  Before doing so, I would often find myself forgetting that I already had written some class which is located deep in some script and recreating it for some other need (granted, composer definitely helped in this regard, but using it wasn't always applicable).

<?php

$c=new Pimple\Container(getMySettings());

$c['pdo'] = function ($c) {
    $db = $c['settings']['mysql'];
    return new \PDO(bla);
};

$c['foo'] = function ($c) {
    return new Foo(
        $c->get('pdo')
    );
};

$c['bar'] = function ($c) {
    return new Bar(
        $c->get('foo')
    );
};

It is all good until I find myself needing to create some new instance of some class instead of just passing some common instance to whoever needs it.

class Foo
{
    private $pdo;

    public function __construct(\PDO $pdo)
    {
        $this->pdo=$pdo;
    }

    public function getSomething():SomeClass
    {
        return new SomeClass($this->getAllDataFromDB($GET['id']));
    }
}

class SomeClass
{
    private $arr;

    public function __construct(array $records)
    {
        foreach($records as $record) {
            $arr[]=new SomeOtherClass($record);
        }
    }
}

I've read that one shouldn't create new objects in a given class's constructor, and while I could instead do so in some class's method and pass the object to the given class's constructor, to me it seems to really be the same thing.  The three issues I have with this scenario a

Are there other compelling reasons not to do so?  Is it worth the effort to do differently?

If so, how would you recommend doing so?  My thoughts would either to use Pimple's factory() method are create my only factory which also relies on anonymous functions.  Maybe something else?

$c['someClass'] = $c->factory(function (array $record, Container $c) {
    return new SomeClass($record);
});

Thanks