PHP code on pages not working in 7.2

[german]

First of all, sorry if I'm not posting in the right place, I'm quite new when it comes to this developing world. 

The truth is that I'm a beginner (very) programmer and I got a job for a local business. I chose to develop their website on prestashop (1.7.4.2, and I'm doing somehow ok, even without understanding the guts of it. 

The reason I'm posting is that in Pages I have built a gallery where products are shown, using a php that gets the info from the database. Since the web is hosted on 1&1 (there are certain things that the owner wants this way) I had to change from php 5.6 to 7.2 since it has no longer support from them. After the change the code I built is no longer giving result. The rest of the website works without apparent problem, but just the code I built is not working. I tested it on online services that check the code and again, apparently, it shows no problem. So I need some community-human based help and I'm too inexperienced yet to know what to do in this case. 

 

I found that the object producto I'm instantiating from the class below is not being created. It happens just in 7.2

 

I paste you here the code from the php:

 

<?php

class producto implements JsonSerializable
{
    private $precio;
    private $nombre;
    private $imagen;

    /**
     * @return mixed
     */
    public function getPrecio()
    {
        return $this->precio;
    }

    /**
     * @param mixed $precio
     */
    public function setPrecio($precio)
    {
        $this->precio = $precio;
    }

    /**
     * @return mixed
     */
    public function getNombre()
    {
        return $this->nombre;
    }

    /**
     * @param mixed $nombre
     */
    public function setNombre($nombre)
    {
        $this->nombre = $nombre;
    }

    /**
     * @return mixed
     */
    public function getImagen()
    {
        return $this->imagen;
    }

    /**
     * @param mixed $imagen
     */
    public function setImagen($imagen)
    {
        $this->imagen = $imagen;
    }

    /**
     * @return mixed
     */
    public function getUrl()
    {
        return $this->url;
    }

    /**
     * @param mixed $url
     */
    public function setUrl($url)
    {
        $this->url = $url;
    }
    private $url;


    public function __construct($nombre,$precio,$imagen,$url)
    {
        $this->precio = $precio;
        $this->nombre = $nombre;
        $this->imagen = $imagen;
        $this->url = $url;
    }

    public function jsonSerialize()
    { return[
        'nombre'=>$this->nombre,
        'precio'=>$this->precio,
        'imagen'=>$this->imagen,
        'url'=>$this->url,
    ];
    }
}

 

Edited February 4, 2019 by german (see edit history)