Question

我正在通过引用此video tutorial: PHP OOP Login/Register System: Database Querying (Part 8/23)来执行登录/注册系统：

我收到错误：

致命错误：调用非对象中的成员函数count（）第6行的C：\ wamp \ www \ login-register-systemv2 \ index.php

的index.php

<?php
require_once 'core/init.php';

$user = DB::getInstance()->get('user', array('username', '=', 'mantas'));

if(!$user->count()) {
    echo 'No user';
} else {
    echo 'Ok';
}

db.php中

这是我的 DB.php ，我认为问题在于：

<?php

class DB {
    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 DB();
        }

        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()) {


        var_dump(count($where));
        if(count($where) === 3) {
            $operators = array('=', '>', '<', '>=', '<=');

            $field      = $where[0];
            $operator   = $where[1];
            $value      = $where[2];

            if(in_array($operator, $operators)) {
                $sql = "{$action} FROM {$table} WHERE {$field} {$operator} {$value} ?";

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

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

}

我找不到有什么问题，也许你可以。

Answer 1

您必须确保您的方法执行始终返回对象。在某些情况下，您的action方法可能会返回false。作为解决方法，您可以将代码更改为：

require_once 'core/init.php';

$db = DB::getInstance();

$user = $db->get('user', array('username', '=', 'mantas'));

if(!$db->count()) {
    echo 'No user';
} else {
    echo 'Ok';
}

Answer 2

$ db = new DB（）; $ user = $ db-＆gt; get（'user'，array（'username'，'='，'mantas'））;

if(!$user->count()) {
    echo 'failed';
} else {
    echo 'success';
}

PHP登录/注册系统错误

的index.php

db.php中

2 个答案: