Fatal error: Call to a member function error() on a non-object

Question

我正在尝试关注来自 phpacademy 的 OOP PHP tutorial，但我被卡住了。我已经无数次检查了代码，但似乎无法弄清楚。其他人也问过类似的问题，但我没有找到适合我的解决方案。

我遇到错误：

Fatal error: Call to a member function error() on a non-object in /var/www/vhosts/nightra.net/httpdocs/index.php on line 5

我对 OOP 比较陌生，所以我确信这是显而易见的。请哪位专家能指出我正确的方向吗？

这是我的代码：

index.php

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

$user = DB::getInstance()->get('users', array('username', '=', 'alex'));
if($user->error()){
    echo 'No user';
}else{
    echo 'OK'; 
}

init.php

<?php
session_start();

$GLOBALS['config'] = array(
        'mysql'=>array(
            'host' => '127.0.0.1',
            'username' => 'myusernamehere',
            'password' => 'mypasswordhere',
            'db' => 'mydatabasename'
        ),
        'remember'=>array(
            'cookie_name' =>'hash',
            'cookie_expiry' => 604800
        ),
        'session'=>array(
            'session_name' => 'user'
        )
);

spl_autoload_register(function($class) {
    require_once 'classes/' . $class . '.php';
});

require_once 'functions/sanitize.php';

DB.php

<?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, $where = array()){
        if(count($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;
    }
 }

Config.php

<?php
class Config {
    public static function get($path = null){
        if($path){
            $config = $GLOBALS['config'];
            $path = explode('/', $path);

            foreach($path as $bit){
                if(isset($config[$bit])){
                    $config = $config[$bit];
                }
            }

            return $config;
        }

        return false;
    }
}

Answer 1

查看 index.php 和 DB.php

的代码

$user 的值来自 BD::get 方法，return 来自 DB::action 方法的值可能是 returning false, 所以你需要测试 $user 是否是 false.

此时您还应该在数据库上手动测试查询。并尝试获取 PDO 错误（如果有）。

Answer 2

以上答案正确 查看整个代码数组 $where 在单引号内访问实际上它应该是 $field = $where[0]; 与数组的其余元素类似 where