Making plugin to use different table prefix cause permission problem

Question

I have multiple wordpress websites that uses the same files and database but with different table prefixes, I use a plugin "Shortcode Exec PHP" and I would like to use the same shortcodes on all the sites, but this plugin doesn't use it's own table, it used the update_option function from wp to store the data.

So I tried just adding this on top of the plugin's code:

$wpdb->prefix = "mainsiteprefix_";

But I get the error:

You do not have sufficient permissions to access this page.

On all the admin pages of the sites that don't uses that prefix and have the plugin activated.

So, how could I make the plugin to use any db prefix I want without having permission problems?

Answer 1

You will need to restore the database prefix after using it , with something like this

global $wpdb;
$previousPrefix=$wpdb->prefix;
$wpdb->prefix="mainsiteprefix_";
//Database access goes here
$wpdb->prefix=$previousPrefix;

or you can create a new wpdb object like this:

$wpdb2 = new wpdb( DB_USER, DB_PASSWORD, DB_NAME, DB_HOST );