php pdo 数据库连接 class

Question

<?php

    class DB_Handler{

        private $host;
        private $db_name;
        private $db_username;
        private $db_password;
        public $dbh;

        public function __construct( $db_host, $db_name, $db_username, $db_password ){

            $this->host = $db_host;
            $this->db_name = $db_name;
            $this->db_username = $db_username;
            $this->db_password = $db_password;
        }

        public function connect(){
            try{                
                $this->dbh = new PDO("mysql:host=$this->host; db_name =$this->db_name, $this->db_username, $this->db_password");

                $this->dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            }
            catch(PDOException $e){
                $error = "Error: ".$e->getMessage().'<br />';
                echo $error;
                return false;
            }
            return true;
        }   

    }

    $db_host = "localhost";
    $db_name = "db_handler_01";
    $db_username = "root";
    $db_password = "sd";

    $snowboard_db = new DB_Handler($db_host, $db_name, $db_username, $db_password);

    $result = $snowboard_db->connect();



    if($result){
        echo "DB Connected <br>";
        echo $snowboard_db;
    }
    else{
        echo "DB is not Connected <br />";      
    }

?>

无论我给出的数据库详细信息是对还是错，它都只显示已连接的数据库。请让我知道我哪里做错了。

Answer 1

这里有两个可能的问题。

第一个已经提到了，你需要将用户名和密码作为PDO构造函数的第二个和第三个参数发送。由于 - 可能放错了 - 引号，您正在发送第一个参数中的所有内容。

第二个问题是您告诉 PDO 在建立（或试图建立）连接后抛出异常。对于可能迟到的连接错误。

如果您还想捕获连接错误，您可以将第四个参数发送到具有所需选项的 PDO 构造函数：

$opt = array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION);
$this->dbh = new PDO("mysql:host={$this->host}; db_name ={$this->db_name}", 
                     $this->db_username, $this->db_password, $opt);

Answer 2

$this->dbh = new PDO("mysql:host=$this->host; db_name =$this->db_name,
                      $this->db_username, $this->db_password");

语法不正确（你弄乱了最后的 "）

正确的语法是：

$this->dbh = new PDO("mysql:host=$this->host;db_name=$this->db_name",
                          $this->db_username, $this->db_password);

顺便说一句，你不能回应你的 class，它会 return :

Catchable fatal error: Object of class DB_Handler could not be converted to string in C:...\index.php on line 49

来源： PHP.net : PDO connections

php pdo 数据库连接 class

php pdo db connection class

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