数据库连接可用于所有类文件

我有一些困惑，我认为

我正试图让我的数据库连接对我的类文件中的函数可用，这样我就不需要把它注入到所有函数的调用中。我认为这是最简洁的方法，但我不确定的反弹

（简化）我有3个文件

1.）数据库连接文件（使用PDO）

2.）类文件与我的所有相关功能

3.）一个主要是HTML文件的文件，该文件包括所需的类和数据库连接，并启动所需的实例。

我的（简化/精简）类文件

<?php
class SPD_Products {
    // varaibales

    // start category variables
    public $CategoryID;
    public $CategoryName;
    public $CategoryDescription;
    public $CategoryActive;
    public $CategoryDateAdded;
    public $CategoryDateModified;

    /*
    * public function to set category varaiables
    * @param int $categoryID
    * @return true/false
    */
    public function setCategory($CategoryID){
        try {
            if(isset($CategoryID) && is_int($CategoryID)){
                if($result = $this->getCategoryByCategoryID($CategoryID)){
                    $this->CategoryID = intval($result->CategoryID);
                    $this->CategoryName = htmlentities($result->CategoryName);
                    $this->CategoryDescription = htmlentities($result->CategoryDescription);
                    $this->CategoryActive = intval($result->CategoryActive);
                    $this->CategoryDateAdded = intval($result->CategoryDateAdded);
                    $this->CategoryDateModified = intval($result->CategoryDateModified);
                }
                else {
                    return 'No Category';
                }           
            }
            else {
                return false;       
            }
        }
        catch (Exception $e){       
            error_log('file = '.__FILE__.'.php class = '.get_class($this).' - function = '.__FUNCTION__.' - Exception caught: '.$e->getMessage());
            return false;   
        }
    }


    /* ================================================================ */
    /* ======================== SQL Queries =========================== */
    /* ================================================================ */

    /*
    * public function to get all category details by CategoryID
    * @param int $CategoryID
    * @return array of results
    */  
    public function getCategoryByCategoryID($CategoryID) {
        try{
            global $db;
            $query = "SELECT c.CategoryID, c.CategoryName, c.CategoryDescription, c.CategoryActive, c.CategoryDateAdded, c.CategoryDateModified, c.CategoryShopAvailable
                        FROM tCategories c                      
                    WHERE c.CategoryID = ?
                    AND c.CategoryActive = 1
                    AND c.CategoryShopAvailable = 1";
            $stmt = $db->prepare($query);
            $stmt->execute(array($CategoryID));             
            return $stmt->Fetch(PDO::FETCH_OBJ);
        }
        catch (PDOException $ex){
            error_log('file = '.__FILE__.'.php class = '.get_class($this).' - function = '.__FUNCTION__.' - Exception caught: '.$ex->getMessage());
            echo 'file = '.__FILE__.'.php class = '.get_class($this).' - function = '.__FUNCTION__.' - Exception caught: '.$ex->getMessage();
            return false;       
        }   
    }
}
?>

我的数据库连接文件

// database login details
//* Define these so that they can't be changed
DEFINE ('DBUSER', 'xxxxx');
DEFINE ('DBPASS', 'xxxxx');
DEFINE ('DBHOST', '192.168.0.99');
DEFINE ('DBPORT', '3999');
DEFINE ('DBNAME', 'xxxxx');
try {
    $db = new PDO('mysql:host='.DBHOST.'; port='.DBPORT.'; dbname='.DBNAME.'; charset=utf8', DBUSER, DBPASS);       
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 

}
catch(PDOException $ex) {
    echo 'An Error occured! '.$ex->getMessage(); //user friendly message    
    error_log('dbconn.php failed to connect to db - Exception caught: '.$ex->getMessage());
    return false;
}
?>

我的测试页面

<?php
require_once('functions/dbconn.php');
require_once('class/products.class.php'); 
//$db = new Database(); // failed test
$products_obj = new SPD_Products();
$products_obj->setCategory($CategoryID = 1);
echo $products_obj->CategoryName;
?>

我尝试了各种方法将数据库连接到类中，但只有全局方法有效（我认为这不是一个好主意…）。以上确实有效，但我想要一个更好的方法。。。。我最终会有很多单独的类文件，所以不想在每个类文件中建立新的连接，因为我相信我只能这样做一次，而不需要使用全局，也不需要不断地注入它并将它从一个函数传递到另一个函数。

任何建议都将不胜感激！

<?php
// database login details
$config = array('DBUSER'=>'xxxxx',
                'DBPASS'=>'xxxxx',
                'DBHOST'=>'192.168.0.99',
                'DBPORT'=>'3999'
                'DBNAME'=> 'xxxxx');
?>

<?php
class DB {
   function __construct() {
      //some config here
      require_once('functions/config.php');
   }
   function get_connection() {
    try {
    $db = new PDO('mysql:host='.$config['DBHOST'].'; port='.$config['DBPORT'].'; dbname='.$config['DBNAME'].'; charset=utf8'
                  , $config['DBUSER'], $config['DBPASS']);        
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 
    }
    catch(PDOException $ex) {
        echo 'An Error occured! '.$ex->getMessage(); //user friendly message    
        error_log('dbconn.php failed to connect to db - Exception caught: '.$ex->getMessage());
        return false;
    }
    return $db;
   }
}
?>

<?php
class SPD_Products {
   require_once('functions/dbconn.php');
   private $conn;
   ....
   function __construct() {
        $db = new DB();
        $this->conn = $db->get_connection();
   }
    public function getCategoryByCategoryID($CategoryID) {
        try{
            $query = "....";
            $stmt = $this->conn->prepare($query);//here
        .......
        }
        catch (PDOException $ex){
           .....
            return false;       
        }   
    }
}
?>