I have a standalone script in my WordPress installation and I have used the following to load the wpdb object:
define( 'SHORTINIT', true );
require_once( $_SERVER['DOCUMENT_ROOT'] . '/wp-load.php' );
However, my error log outputs the following when I call the script:
PHP Fatal error: Call to undefined function __() in /wp-includes/wp-db.php on line 1297
When I go to line 1297 in wp-db.php, I see
_doing_it_wrong( 'wpdb::prepare', sprintf( __( 'The query argument of %s must have a placeholder.' ), 'wpdb::prepare()' ), '3.9.0' );
If I comment out that line, the script doesn't crash, but being a core WordPress file, I don't think that's the best solution.
I do use the prepare method in a separate class, however it is only at the standalone script file that I get this error. When I re-use that same separate class by creating an object in a file that WordPress "recognizes", I don't get the error.