Question

我在这里遇到PDO :: execute（）的问题。问题是我有3个数据库，我想构建一个Singleton类和一个通用查询方法。所以我的DB类结构是这样的：

class DB{
        private static $_instance = null;
        private $_pdo1, $_pdo2, $_pdo3,
                $_query,
                $_results,
                $_error = false,
                $_count = 0;

        private function __construct(){
            try{
                $dns1 = 'mysql:host='.Config::get('mysql1/host').';dbname='.Config::get('mysql1/dbname').'';
                $dns2 = 'mysql:host='.Config::get('mysql2/host').';dbname='.Config::get('mysql2/dbname').'';
                $dns3 = 'mysql:host='.Config::get('mysql3/host').';dbname='.Config::get('mysql3/dbname').'';
                $username1 = Config::get('mysql1/username');
                $username2 = Config::get('mysql2/username');
                $username3 = Config::get('mysql3/username');
                $password1 = Config::get('mysql1/password');
                $password2 = Config::get('mysql2/password');
                $password3 = Config::get('mysql3/password');
                $this->_pdo1 = new PDO($dns1, $username1, $password1);
                $this->_pdo2 = new PDO($dns2, $username2, $password2);
                $this->_pdo3 = new PDO($dns3, $username3, $password3);
            }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 = $this->_pdo1->prepare($sql) || $this->_query = $this->_pdo2->prepare($sql) || $this->_query = $this->_pdo3->prepare($sql)){
                if(count($params)){
                    $x = 1;
                    foreach($params as $param){
                        $this->_query->bindValue($x, $param);
                        $x++;
                    }
                }
                if($this->_query->execute()){
                    echo "Success";
                }
            }
        }
    }

第49行中的

我收到此错误：

Fatal error: Call to a member function execute() on boolean in /htdocs/DatabaseStructure/classes/DB.php on line 49

第49行：if($this->_query->execute())

也试过但没有成功：

if($this->_query->execute() == TRUE)
if(!$this->_query->execute() == FALSE)

为什么这会给我一个错误？

Answer 1

在query()方法

中查看此行

if($this->_query = $this->_pdo1->prepare($sql) || $this->_query = $this->_pdo2->prepare($sql) || $this->_query = $this->_pdo3->prepare($sql)){ ...

问题是由于逻辑OR条件的错误分组。使用此条件语句$this->_query将始终评估为true或false。

以下是两个示例来说明这一点：

要使其正常工作，请更改条件语句，如下所示：

if(($this->_query = $this->_pdo1->prepare($sql)) || ($this->_query = $this->_pdo2->prepare($sql)) || ($this->_query = $this->_pdo3->prepare($sql))){ ...

所以你的query()方法应该是这样的：

public function query($sql, $params = array()){
    $this->_error = false;
    if(($this->_query = $this->_pdo1->prepare($sql)) || ($this->_query = $this->_pdo2->prepare($sql)) || ($this->_query = $this->_pdo3->prepare($sql))){
        if(count($params)){
            $x = 1;
            foreach($params as $param){
                $this->_query->bindValue($x, $param);
                $x++;
            }
        }
        if($this->_query->execute()){
            echo "Success";
        }
    }
}

要测试代码，请运行如下的简单查询：

DB::getInstance()->query("SELECT * FROM users");

布法上的致命错误execute（）

1 个答案: