Title: Connecting with external database (functions.php?)
Last modified: November 21, 2020

---

# Connecting with external database (functions.php?)

 *  [Klaas Koopman](https://wordpress.org/support/users/inspired-media/)
 * (@inspired-media)
 * [5 years, 6 months ago](https://wordpress.org/support/topic/connecting-with-external-database-functions-php/)
 * Hi everyone,
 * I’ve been working on this for a week now and still can’t find the right answer.
 * My situation:
    I’ve got another database (on same hosting as current site, so
   localhost), which I want to use data of in my theme files.
 *     ```
       $mydatabase = new mysqli("localhost","my_user","my_password","my_db");
   
       // Check connection
       if ($mydatabase -> connect_errno) {
         echo "Failed to connect to MySQL: " . $mydatabase -> connect_error;
         exit();
       }
   
       // Perform query
       if ($result = $mydatabase -> query("SELECT * FROM tableabc WHERE xandy='4'")) { (etc)
       ```
   
 * Above is what is in my single_cpt.php file and that works. But I’ve heard I should
   not have this part in there: `$mydatabase = new mysqli("localhost","my_user","
   my_password","my_db");` and I should use that part in Functions.php. Now i’ve
   tried to remove the above line and add the line below to functions.php, but can’t
   seem to get it to work.
 *     ```
       function connect_another_db() {
           global $my_db;
           $my_db= new wpdb('my_user','my_password','my_db', 'localhost');
       }
       add_action('init', 'connect_another_db');
       ```
   
 * Can someone please help me out, would really appreciate it!

Viewing 3 replies - 1 through 3 (of 3 total)

 *  [Dion](https://wordpress.org/support/users/diondesigns/)
 * (@diondesigns)
 * [5 years, 6 months ago](https://wordpress.org/support/topic/connecting-with-external-database-functions-php/#post-13692787)
 * If you are familiar with using the mysqli functions (OOP or procedural), then
   by all means use them! Using `$wpdb` to connect with a second database introduces
   significant overhead and should IMO be avoided if at all possible.
 * If the WordPress DB user has the access you require to the second database, then
   you can adjust your queries and use the already-existing handle created by the`
   $wpdb` class. The following code will obtain the handle:
 *     ```
       global $wpdb;
       $dbh = $wpdb->__get('dbh');
       ```
   
 * However, keep in mind that you must use `mysqli_*()` procedural commands since
   that is how the handle was created.
 *  Thread Starter [Klaas Koopman](https://wordpress.org/support/users/inspired-media/)
 * (@inspired-media)
 * [5 years, 6 months ago](https://wordpress.org/support/topic/connecting-with-external-database-functions-php/#post-13693442)
 * Dear Dion,
 * Thank you for your reply.
 * So you are saying I can have this part in my themefiles (singlecpt.php for example)
 * `$mydatabase = new mysqli("localhost","my_user","my_password","my_db");`
 * As i’ve been told that’s not a good idea and I should include it somehow into
   my functions.php?
 *  [Dion](https://wordpress.org/support/users/diondesigns/)
 * (@diondesigns)
 * [5 years, 6 months ago](https://wordpress.org/support/topic/connecting-with-external-database-functions-php/#post-13695047)
 * Since the PHP `mysqli` extension is available in all versions of PHP supported
   by WordPress, you can safely ignore those who told you to use new instance of`
   $wpdb`. (I would bet that those same people do not know how to use `mysqli` functions/
   methods and only know how to use `$wpdb` methods. 🙂 )
 * Just make sure to close the DB connection when you’re done with it. PHP will 
   not immediately do so when a script ends, and it is a common cause of “too many
   connections” errors.

Viewing 3 replies - 1 through 3 (of 3 total)

The topic ‘Connecting with external database (functions.php?)’ is closed to new 
replies.

 * In: [Fixing WordPress](https://wordpress.org/support/forum/how-to-and-troubleshooting/)
 * 3 replies
 * 2 participants
 * Last reply from: [Dion](https://wordpress.org/support/users/diondesigns/)
 * Last activity: [5 years, 6 months ago](https://wordpress.org/support/topic/connecting-with-external-database-functions-php/#post-13695047)
 * Status: not resolved

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