如何在所有PHP页面中统一定义$db数据库连接变量？

Great question! Duplicating database connection logic across multiple files is a common pain point—let's clean this up by centralizing the connection into a single reusable file, so you only write that code once.

Here's the step-by-step solution: #

1. Create a centralized database connection file
   Make a new file named db-connect.php (you can use any name that fits your project structure) and move all the duplicate connection code into it:

   // db-connect.php
   // Connect to the database server and select database.
   $db = createDatabaseConnection($db_type, $db_host, $db_user, $db_pass, $db_name, $table_prefix);
   if (!$db instanceof KEYDatabase) {
       die(get_lang('no_db_connection'));
   }
   

2. Update show.php to use the centralized connection
   Remove the duplicate connection code from show.php and include the shared connection file at the top:

   // show.php
   // Include the shared database connection
   require_once 'db-connect.php';
   
   $result = $db->Show_keys();
   foreach ($result as $row) {
       echo $row['key_value'] . "<br>";
   }
   

3. Update generate.php the same way
   Strip out the duplicate connection code from generate.php and include the shared file:

   // generate.php
   // Include the shared database connection
   require_once 'db-connect.php';
   
   $key_value = serialkey();
   $key_balance = 10;
   $key_created_date = date("Y-m-d h:m:s");
   if ($db->addkey($key_value, $key_balance, $key_created_date)) {
       echo 'New Key added to database!<br>' . $key_value;
   }
   

Bonus: Centralize your configuration variables too #

If your $db_type, $db_host, $db_user, etc., are also duplicated across files, you can take this a step further by moving those into a separate config.php file:

// config.php
$db_type = 'your_database_type';
$db_host = 'your_host_address';
$db_user = 'your_db_username';
$db_pass = 'your_db_password';
$db_name = 'your_database_name';
$table_prefix = 'your_table_prefix';

Then update db-connect.php to include this config file first:

// db-connect.php
require_once 'config.php';

$db = createDatabaseConnection($db_type, $db_host, $db_user, $db_pass, $db_name, $table_prefix);
if (!$db instanceof KEYDatabase) {
    die(get_lang('no_db_connection'));
}

Why this works: #

• require_once ensures the connection file is only loaded once, even if you accidentally include it multiple times (preventing duplicate connection attempts).
• It eliminates code duplication entirely—any future changes to your database connection logic only need to be made in one place.
• It keeps your show.php and generate.php focused on their specific tasks, rather than handling connection boilerplate.

内容的提问来源于stack exchange，提问作者Amin Hijaz