php 创建数据库连接类 (PDO) 并获取数据
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Creating a database connection class (PDO) and fetch data
提问by black_belt
I am new to OOP, so I am trying to learn how to create classes and use them. Currently I am trying to fetch data from my MySQL table.
我是 OOP 的新手，所以我正在尝试学习如何创建类并使用它们。目前我正在尝试从我的 MySQL 表中获取数据。
To create the connection with MySQL I am using PDO. I have created a separate class for database connection. I have included the class in my show.php file. Now I want to fetch data from MySQL database. The problem is when I run my show.php file it shows this error message
要创建与 MySQL 的连接，我正在使用 PDO。我为数据库连接创建了一个单独的类。我已经在我的 show.php 文件中包含了这个类。现在我想从 MySQL 数据库中获取数据。问题是当我运行我的 show.php 文件时它会显示此错误消息
Fatal error: Call to undefined method DBConnection::prepare() in C:\xampp\htdocs\jm\show.php on line 10`
致命错误：调用 C:\xampp\htdocs\jm\show.php 中第 10 行的未定义方法 DBConnection::prepare()`
But it was supposed to display just array.
但它应该只显示array.
What is the solution to this problem?
这个问题的解决方案是什么？
File db.class.php
文件db.class.php
<?php
class DBConnection {
function DBConnection(){
$host = 'localhost';
$dbname = 'srijon';
$user = 'root';
$pass = '';
try {
$DBH = new PDO("mysql:host=$host;dbname=$dbname", $user, $pass);
$DBH->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
return $DBH;
}
catch(PDOException $e) {
echo 'ERROR: ' . $e->getMessage();
}
} // function ends
} // class ends
?>
File show.php
文件show.php
<?php
require_once 'db.class.php';
function get_all(){
$db = new DBConnection();
$sql = "SELECT * FROM information";
$STH = $db->prepare($sql);
$STH->execute();
$STH->setFetchMode(PDO::FETCH_ASSOC);
return $STH;
}
echo get_all();
?>
回答by PeeHaa
IMHO you can just inject the PDO connection into the functions that need it:
恕我直言，您可以将 PDO 连接注入到需要它的函数中：
<?php
$dbHandle = new PDO("mysql:host=$host;dbname=$dbname", $user, $pass);
$dbHandle->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
// always disable emulated prepared statement when using the MySQL driver
$dbHandle->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
function get_all($dbHandle) {
$sql = "SELECT * FROM information";
$stmt = $dbHandle->prepare($sql);
$stmt->execute();
$stmt->setFetchMode(PDO::FETCH_ASSOC);
return $stmt;
}
get_all($dbHandle);
If you really think you need some class to access to database (other than PDO) (which you don't need) you would have to extend PDO:
如果您真的认为您需要某个类来访问数据库（PDO 除外）（您不需要），则必须扩展 PDO：
<?php
class DBConnection extends PDO
{
public function __construct()
{
parent::__construct("mysql:host=$host;dbname=$dbname", $user, $pass);
$this->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
// always disable emulated prepared statement when using the MySQL driver
$this->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
}
}
$dbHandle = new DBConnection();
function get_all($dbHandle) {
$sql = "SELECT * FROM information";
$stmt = $dbHandle->prepare($sql);
$stmt->execute();
$stmt->setFetchMode(PDO::FETCH_ASSOC);
return $stmt;
}
get_all($dbHandle);
回答by Prash
Maybe change the DBConnections FUNCTION to a __contstruct() function. In addition, you'd need to extend the PDO class to use all the methods within it.
也许将 DBConnections FUNCTION 更改为 __contstruct() 函数。此外，您需要扩展 PDO 类以使用其中的所有方法。
