致命错误：在布尔上调用成员函数rowCount（）。 PHP的PDO

Question

我正在用php（pdo）创建一个登录系统，我正在

  

Blockquote   致命错误：未捕获错误：在C：\ xampp \ htdocs \ user_login_system \ index.php：4中的bool上调用成员函数count（）：4堆栈跟踪：＃0 {main}抛出在C：\ xampp \ htdocs \ user_login_system \第4行的index.php   引用

Index.php

<?php
require_once 'core/init.php';
$user = DBH::getInstance()->get('users', array('username', '=', 'Brye'));
if (!$user->count()){
   echo 'No user';
}else{
    echo 'OK';
}

DBH.php

<?php

class DBH {
    private static $_instance = null;
    private $_pdo, $_query, $_error = false, $_results, $_count = 0;

    private function __construct() {
        try {
            $this->_pdo = new PDO('mysql:host='  . Config::get('mysql/host').  '; dbname='.Config::get('mysql/db'), Config::get('mysql/username'), Config::get('mysql/password'));
        } catch (PDOException $e) {
            die($e->getMessage());
        }
    }

    public static function getInstance() {
        if (!isset(self::$_instance)) {
            self::$_instance = new DBH();
        }
        return self::$_instance;
    }

    public function query($sql, $params = array()) {
        $this->_error = false;
        if ($this->_query = $this->_pdo->prepare($sql)) {
            $x = 1;
            if (count($params)) {
                foreach ($params as $param) {
                    $this->_query->bindValue($x, $param);
                    $x++;
                }
            }
            if ($this->_query->execute()) {
                $this->_results = $this->_query->fetchAll(PDO::FETCH_OBJ);
                $this->_count = $this->_query->rowCount();
            } else {
                $this->_error = true;
            }
        }
        return $this;
    }

    public function action($action, $table, $where = array()) {
        if (count($where) === 3) {
            $operators = array('=', '>', '<', '=>', '<=');
            $field = $where[0];
            $operator = $where[1];
            $value = $where[2];

            if (in_array($operator, $operators)) {
                $sql = "{action} FROM {$table} WHERE {$field} {$operator} ?";
                if (!$this->query($sql, array($value))->error()) {
                    return $this;
                }
            }
        }
        return false;
    }

    public function get($table, $where) {
        return $this->action('SELECT *', $table, $where);
    }

    public function delete($table, $where) {
        return $this->action('DELETE', $table, $where);
    }

    public function error() {
        return $this->_error;
    }

    public function count() {
        return $this->_count;
    }
}