Question

我正在尝试从程序PHP切换到OO PHP。

我创建了一个看起来像这样的Db类：

   class Db {

       protected static $connection;

       /*
       Attempt to connect to database. 

       @Return bool false on failure, mysqli object instance on success

       */

       public function connect() {

           if(!isset(self::$connection)) {

                //Parse DB info from configuration file
                $config = parse_ini_file('../validconfigpath/config.ini');

                //Attempt to connect to the datbase
                self::$connection = new mysqli($config['dbhost'], $config['dbuser'], $config['dbpass'], $config['dbname']);


                if(self::$connection === false) {
                    //Database connection unsuccessful, how to handle?
                    echo "Error connecting to database.<br />";
                    return false;
                }

                return self::$connection;
           }
       }

       /*
        * Query the database
        * @param $query The sql string
        * @return mixed The result of the mysqli::query() function
        */

       public function query($query) {
           //Connect to the database
           $connection = $this -> connect();

           //Query the database
           $result = $connection -> query($query);

           return $result;
       }

       /*
        * Fetch rows from the database (SELECT query)
        * @param $query The query string
        * @return bool false on failure / array Database rows on success
        * 
        */

       public function select($query) {
           $rows = array();
           $result = $this -> query($query);

           if ($result === false) {
               return false;
           }

           while($row = $result -> fetch_assoc()) {
               $rows[] = $row;
           }

           return $rows;

       }

       /*
        * Fetch last inserted ID from the database
        * @return ID of last inserted record using this connection, or 0 if no INSERT or UPDATE statements were sent
        */

       public function inserted_id() {

           $connection = $this -> connect();

           return $connection -> insert_id;

       }

       public function quote($value) {

           $connection = $this -> connect();

           return "'" . $connection -> real_escape_string($value) . "'";
       }


   }

我正在尝试使用以下代码测试quote函数：

include_once 'Classes/DB.php';

$db = new Db();

$firstName = $db -> quote("First");
echo $firstName. "<br />";


$lastName = $db -> quote("Last");
echo $lastName. "<br />";

我得到了$firstName的预期输出，如下所示：

'First'

但是对于我$lastName的第二个输出，我得到了：

Fatal error: Uncaught Error: Call to a member function real_escape_string() on null in ..\Classes\DB.php:91 Stack trace: #0 ..\index.php(11): Db->quote('Last') #1 {main} thrown in ..\Classes\DB.php on line 91

我尽可能地告诉$connection发生了一些事情，但我无法弄清楚connect()出了什么问题。

此外，我认为最好在__construct中创建一个连接？

Answer 1

connect（）方法中存在错误。此方法仅返回第一个连接实例。对connect（）的第二次调用将返回null。尝试移动return self :: $ connection;到这个方法的最后一行。

public function connect()
{
    if (!isset(self::$connection)) {

        //Parse DB info from configuration file
        $config = parse_ini_file('../validconfigpath/config.ini');

        //Attempt to connect to the datbase
        self::$connection = new mysqli($config['dbhost'], $config['dbuser'], $config['dbpass'], $config['dbname']);

        if (self::$connection === false) {
            //Database connection unsuccessful, how to handle?
            echo "Error connecting to database.<br />";
            return false;
        }
    }

    return self::$connection;
}

如何在null＆＃39;上修复＆＃39;调用成员函数real_escape_string（）？

1 个答案: