namespace models;
use PDO;
class Conexion{
private $host = "localhost";
private $user = "root";
private $pass = "";
private $dbname = "veterinaria";
private $charset = "utf8";
private $port = 3306;
private $conexion = null;

public function __construct()
{
    try {
        $dsn = "mysql:host={$this->host};dbname={$this->dbname};charset={$this->charset};port={$this->port}";
        $this->conexion = new PDO($dsn, $this->user, $this->pass, array(
        PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
        PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_EMULATE_PREPARES   => FALSE
    ));
    } catch (PDOException $ex) {
        print $ex->getMessage();
        print $ex->getCode();
        print_r($ex->getTrace());
        print $ex->getLine();
    }
}

namespace models;
use PDO;
require('Conexion.php');
class Paciente{
private $id_paciente;
private $fk_tipo;
private $nombre;
private $edad;
private $foto;
private $c_vacunacion;
private $fk_dueño;
private $peso;
private $conexion;

public function __construct()
{
    $this->conexion = new Conexion();
}

public function retornarPaciente(int $id_paciente):array
{
    $sql = "SELECT id_paciente, nombre, edad, foto, peso FROM paciente WHERE id_paciente = :id";
    $stmn = $this->conexion->get()->prepare($sql);
    $stmn->bindParam(":id", $id_paciente, PDO::PARAM_INT);
    $stmn->execute();
    return $stmn->fetch();
}