Is it possible to validate before creating an object in PHP?

Question:

I have the following doubt: is it possible to validate the shape of an array before creating an object?

I have the following scenario. I am creating an apiRest and the programmer that consumes my API sends me a message with the following JSON:

[
  {
    "Codigo":"1",
    "Nombre":"NESTEA",
    "Presentacion":"1.5 L",
    "Foto":"http://localhost/api/public/img/pepsi.jpg",
    "MarcaId":"1",
    "FamiliaId":"1",
    "ProveedorId":"2",
    "Rating":"5",
    "Estado":"0"
  }
]

In the apiRest I implemented a post method and it must create a new object with the JSON converted into an array:

 if($_SERVER['REQUEST_METHOD']=='POST'){
     $postBody = file_get_contents("php://input");
     $jsonToArray = json_decode($postBody,true);

     $producto = new productos($jsonToArray);

     print_r($producto->getCodigo());
     http_response_code(200);
  }

Class code:

class productos {
     //atributos
     private $Codigo;
     private $Nombre;
     private $Presentacion;
     private $Foto;
     private $MarcaId;
     private $FamiliaId;
     private $ProveedorId;
     private $Rating;
     private $Estado;

     //constructor
     public function productos($array){
            $this->Codigo = $array[0]['Codigo'];
            $this->Nombre = $array[0]['Nombre'];
            $this->$Presentacion = $array[0]['Presentacion'];
            $this->Foto = $array[0]['Foto'];
            $this->MarcaI = $array[0]['MarcaId'];
            $this->FamiliaId = $array[0]['FamiliaId'];
            $this->ProveedorId = $array[0]['ProveedorId'];
            $this->Rating = $array[0]['Rating'];
            $this->Estado = $array[0]['Estado'];
     }

     public function GuardarProducto(){
         return $this->Codigo;
     }
}

So far everything is fine. The problem arises when they stop sending me a parameter. For example:

[
  {
    "Codigo":"1",
    "Nombre":"NESTEA",
    "Presentacion":"1.5 L",
    "Foto":"http://localhost/api/public/img/pepsi.jpg",
    "MarcaId":"1",
    "FamiliaId":"1",
    "ProveedorId":"2",  
  }
]

I get the following error:

Notice : Undefined variable: Presentacion in C: \ xampp \ htdocs \ api \ objects \ products.php on line 21

Fatal error : Cannot access empty property in C: \ xampp \ htdocs \ api \ objects \ products.php on line 21

The only thing I can think of is to use if(isset(array[0]['Estado']){ //validar } , but I want all the fields to be required and send a 400 error to the programmer if the POST is not correct.

How could I do it?

Answer:

Just like you said, with isset() and then the header() function to send you the error response.

In the file where you receive the data you could use a try/catch block and there handle the error status. Something like that:

try {
   $postBody = file_get_contents("php://input");
   $jsonToArray = json_decode($postBody,true);

   $producto = new productos($jsonToArray);

   print_r($producto->getCodigo());
   http_response_code(200);

} catch (Exception $e) {
   header('HTTP/1.1 400 ' . $e->getMessage());
}

And in the class throw an exception when some validation fails:

if (!isset($array[0]['Estado'])) {
   throw new Exception('El campo Estado es obligatorio');
}