我正在尝试执行一个看起来很简单的操作，但却出现了一个奇怪的错误
未捕获的异常：'PDO异常'
消息："SQLSTATE [HY000]：一般错误：无法调用类构造函数"
堆栈跟踪：

0 C:\xampp\htdocs\hotel\Core\Model.php(48): PDOStatement->fetch()
1 C:\xampp\htdocs\hotel\App\Controllers\Admin\Rooms.php(188): Core\Model::findById('98')***
2 C:\xampp\htdocs\hotel\Core\Router.php(78): App\Controllers\Admin\Rooms::deletePhoto()
3 C:\xampp\htdocs\hotel\public\index.php(62): Core\Router->dispatch('admin/rooms/del...')
4 {main}**

在第48行的"C：\xampp\htdocs\酒店\核心\模型. php"中抛出
这是导致此错误的函数。

public static function findById($id){

        $sql = 'SELECT * FROM ' . static::$db_table . ' WHERE id = :id';
        $db = static::getDB();
        $statement = $db->prepare($sql);
        $statement->bindParam(':id', $id, PDO::PARAM_INT);
        $statement->setFetchMode(PDO::FETCH_CLASS, get_called_class());

        $statement->execute();

        return $statement->fetch();
    }

我已经检查了composer.json psr-4部分，它看起来像所有的目录与我的类都在那里。那么为什么我会得到这个错误？
这是包含该方法的整个类

namespace Core;

use PDO;
use App\Config;
abstract class Model {

protected static function getDB()
{
    static $db = null;

    if ($db === null) {

        $dsn = 'mysql:host=' . Config::DB_HOST . ';dbname=' .
            Config::DB_NAME . ';charset=utf8';
        $db = new PDO($dsn, Config::DB_USER, Config::DB_PASSWORD);

        // Throw an exception when an error occurs
        $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    }
    return $db;
}

// finds everything by ID (photo, user, booking)
public static function findById($id){

    $sql = 'SELECT * FROM ' . static::$db_table . ' WHERE id = :id';
    $db = static::getDB();
    $statement = $db->prepare($sql);
    $statement->bindParam(':id', $id, PDO::PARAM_STR);
    $statement->setFetchMode(PDO::FETCH_CLASS, '\App\Models\Admin\Photo');

    $statement->execute();

    return $statement->fetch();
}

// this method deletes via id
public static function delete($id){

    $sql = 'DELETE FROM ' . static::$db_table . ' WHERE ' . static::$column .  ' = :id';

    $db = static::getDB();
    $statament = $db->prepare($sql);

    $statament->bindValue(':id', $id, PDO::PARAM_STR);
    return $statament->execute();
}

// returns everything from selected database table
public static function findAll(){

    $sql = 'SELECT * FROM ' . static::$db_table;

    $db  = static::getDB();
    $stm = $db->prepare($sql);
    $stm->setFetchMode(PDO::FETCH_CLASS, get_called_class());

    $stm->execute();

    return $stm->fetchAll();
}


}

这是我的摄影课：'命名空间应用\模型\管理;

use PDO;
use \App\Config;

class Photo extends \Core\Model {

public $errors_on_upload = [];                          // array for saving error messages
public static $db_table = 'photos';                     // database table
public static $column = 'id';
protected static $upload_derictory = 'public\uploads\pictures\rooms'; // path to uploaded pictures
protected static $path = '/uploads/pictures/rooms';
protected static $path_to_unlink = 'uploads/pictures/rooms/';
public $upload_errors_array = array(

    UPLOAD_ERR_OK            => "There is no errors",
    UPLOAD_ERR_INI_SIZE      => "The uploaded file exceeds max size",
    UPLOAD_ERR_FORM_SIZE     => "The uploaded file exceeds max size of form post request",
    UPLOAD_ERR_PARTIAL       => "The uploaded file was only partially uploaded",
    UPLOAD_ERR_NO_FILE       => "No file was uploaed",
    UPLOAD_ERR_NO_TMP_DIR    => "Missing the temporary folder",
    UPLOAD_ERR_CANT_WRITE    => "Failed to write to disk",
    UPLOAD_ERR_EXTENSION     => "A php extension stopped the file upload",

);

// supplied with $_FILES and input name of multiply input file
public function __construct($picture) {

        // here we creates properties and their values out of keys and values
        foreach($picture as $key => $value){
            $this->$key = $value;
            //echo $key;
        }

}

// creates a easy-readable array of properties and their values out of multiply-files array from form
// must be supplied with argument in format $_FILES['input_name']
public static function reArrayFiles($file_post) {

    $file_ary = array();
    $file_count = count($file_post['name']);
    $file_keys = array_keys($file_post);

    for ($i=0; $i < $file_count; $i++){
        foreach ($file_keys as $key){
            $file_ary[$i][$key] = $file_post[$key][$i];
        }
    }

    return $file_ary;
}

// this function saves photos to the database
public function save($room_id, $i){

    // first validate uploaded file
    $this->validatePhoto();

    if(empty($this->errors_on_upload)){ // insert data only if array with errors is empty

        $this->filename = time() . $this->name;

        $sql = 'INSERT INTO ' . static::$db_table . ' (room_id, main, name, type, size, path) VALUES (:room_id, :main, :name, :type, :size, :path)';
        $db  = static::getDB();

        $stm = $db->prepare($sql);

        $i = ($i === 0) ? true : false;

        $stm->bindValue(':room_id', $room_id, PDO::PARAM_INT);
        $stm->bindValue(':main', $i, PDO::PARAM_INT);
        $stm->bindValue(':name', $this->filename, PDO::PARAM_STR);
        $stm->bindValue(':type', $this->type, PDO::PARAM_STR);
        $stm->bindValue(':size', $this->size, PDO::PARAM_INT);
        $stm->bindValue(':path', $this->pathToPicture(), PDO::PARAM_STR);

        $stm->execute();

        $target_path = dirname(__DIR__, 3) . Config::DS . static::$upload_derictory . Config::DS . $this->filename;
        if(file_exists($target_path)){
            $this->errors_on_upload[] = 'This file already exists in this directory';
            return false;
        }

        if( !empty($this->tmp_name)){ // if tmp_name is empty, we just don't upload files

            if( ! move_uploaded_file($this->tmp_name, $target_path)){
                $this->errors_on_upload[] = 'The folder probably doesnt have permissions';
            } else {
                return true;
            }

        }

    }
    return false; // on failure
}


// this method validates pictures on upload
protected function validatePhoto(){

    $extension = $this->type;

    if( !empty($extension)){
        if($extension != 'image/jpeg' && $extension != 'image/png' && $extension != 'image/jpg'){
            $this->errors_on_upload[] = "Your file should be .jpeg, .jpg or .png";
        }
    }

    if($this->size > Config::MAX_FILE_SIZE){
        $this->errors_on_upload[] = "Your picture shouldn't be more than 10 Mb";
    }

    if($this->error != 0 && $this->error != 4) { //0 means no error, so if otherwise, display a respective message, 4 no files to upload, we allow that
        $this->errors_on_upload[] = $this->upload_errors_array[$this->error];
    }

}


protected function pathToPicture(){
    return static::$path . Config::DS . $this->filename;
}



public static function findAllPhotosToONeRoom($room_id, $main_photo_only){

    $sql  = 'SELECT * FROM photos WHERE room_id = :id'; // we need to pass only the main picture to all_rooms template
    $sql .= $main_photo_only ? ' AND main = 1' : '';    // get only main photo or all

    $db  = static::getDB();

    $stm = $db->prepare($sql);

    $stm->bindValue(':id', $room_id, PDO::PARAM_INT);


    if(($stm->execute())){

        if($main_photo_only){        // fetch all or only one row (for all_rooms page or for a particular room page)

            $pictures = $stm->fetch();

            return $pictures;

        } else {
            $pictures = $stm->fetchAll();

            return $pictures;
        }


    } else {
        // return a sample array with placeholder on failure instead of false to avoid further use 'false' as an array
        return false;
    }

}

// sets photo as a main by id and unsets prev main one
public static function setPictureAsMain($picture_id, $room_id){

    // check whether id's were supplied by AJAX request
    if($picture_id !== null && $room_id !== null){

        // first set old main photo main column to 0
        if(static::unsetMainPhoto($room_id)){

            // set chosen photo as main
            $sql = 'UPDATE ' . static::$db_table . ' SET main = 1 WHERE id = :picture_id';
            $db  = static::getDB();

            $stm = $db->prepare($sql);
            $stm->bindValue(':picture_id', $picture_id, PDO::PARAM_INT);

            return $stm->execute();

        }

    }

     return false;

}

// unsets main photo of a room
public static function unsetMainPhoto($room_id){

    $sql = 'UPDATE ' . static::$db_table . ' SET main = 0 WHERE room_id = :room_id AND main = 1';
    $db  = static::getDB();

    $stm = $db->prepare($sql);
    $stm->bindValue(':room_id', $room_id, PDO::PARAM_INT);

    return $stm->execute();
}

// this method adds photos to an existing room
public static function addPhotos($room_id, $pictures){

    // array for errors
    $errors_on_update = array();

    foreach ($pictures as $picture){

       if($picture->save($room_id, true)){

           $errors_on_update[] = true;

       }

    }

    return in_array(0, $errors_on_update, false) ? false : true;

}

// this method deletes images from upload folder
public static function unlinkImages($filename){
    return unlink(static::$path_to_unlink . $filename);
}


}`