在PHP中的类中使用全局DB变量 [英] using global DB variable inside classes in PHP

问题描述

如何在类中使用全局数据库变量？
假设我在我的config.php中有这个

  $ dbh = new PDO（mysql：host = localhost ; dbname = mydb，root，）; 
  

并且我想在类中使用这个$ dbh如下（MyClass.php）

  class MyClass 
 {
 public function DoSomething（$ plogin_id）
 {
 $ s $ = SELECT * FROM mytable WHERE login_id =：login_id; 
 $ stmt = $ dbh-> prepare（$ sql）; // line 14 
 $ stmt-> bindParam（'：login_id'，$ plogin_id，PDO :: PARAM_STR）; 
} 
} 
  

在我的index.php文件中， MyClass如下：

  includeconfig.php; 
 $ MyObject = new MyClass（）; 
 $ login_result = $ MyObject-> DoSomething（admin）; 
  

它给我错误：

致命错误：调用成员函数
对
中的非对象执行prepare（）C：\ xampp\htdocs\MyProject\admin\includes\\ \\ classes \MyClass.php
第14行

解决方案

将 $ dbh 对象传递给 MyClass 。由于你不想使用全局变量，我建议你将它传递给 MyClass 的构造函数。

您的MyClass和index.php可能如下所示：

  class MyClass 
 {
 protected $ dbh = null; 
 
 public function __construct（PDO $ Pdh）
 {
 $ this-> dbh = $ Pdh; 
} 
 
 public function DoSomething（$ plogin_id）
 {
 $ sql =SELECT * FROM mytable WHERE login_id =：login_id; 
 $ stmt = $ this-> dbh-> prepare（$ sql）; // line 14 
 $ stmt-> bindParam（'：login_id'，$ plogin_id，PDO :: PARAM_STR）; 
} 
} 
 
 // in your index.php 
 $ MyObject = new MyClass（$ dbh）; 
  

这基本上是一种称为依赖注入的模式。有关这是什么的更多信息，请参见这个出色的教程。 p>

How can I use global DB variable inside class? Let's say I have this in my config.php

$dbh = new PDO("mysql:host=localhost;dbname=mydb", "root", "");

and I want to use this $dbh inside class as follows (MyClass.php)

class MyClass
{
   public function DoSomething($plogin_id)
   {
        $sql = "SELECT * FROM mytable WHERE login_id = :login_id";      
        $stmt = $dbh->prepare($sql);    //line 14
        $stmt->bindParam(':login_id', $plogin_id, PDO::PARAM_STR);
   }
}

And inside my index.php file I am using this MyClass as follows:

include "config.php";
$MyObject = new MyClass();
$login_result = $MyObject->DoSomething("admin");

It is giving me error:

Fatal error: Call to a member function prepare() on a non-object in C:\xampp\htdocs\MyProject\admin\includes\classes\MyClass.php on line 14

解决方案

You have to pass the $dbh object to MyClass somehow. Since you don't want to use globals, I suggests you pass it to MyClass's constructor.

Your MyClass and index.php could look something like this:

class MyClass
{
   protected $dbh = null;

   public function __construct ( PDO $Pdh )
   {
      $this->dbh = $Pdh;
   }

   public function DoSomething($plogin_id)
   {
        $sql = "SELECT * FROM mytable WHERE login_id = :login_id";      
        $stmt = $this->dbh->prepare($sql);    //line 14
        $stmt->bindParam(':login_id', $plogin_id, PDO::PARAM_STR);
   }
}

// in your index.php
$MyObject = new MyClass ( $dbh );

This is basically a pattern called dependency injection. See this excellent tutorial for more info on what this is.

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