Create WordPress Admin Account Using FTP/PHP
April 25, 2012
Here is a little snippet which can create a WordPress backend account with ease using the FTP, just paste this PHP snippet in the active theme’s functions.php and the account will be created. Also, make sure the username and the email are unique, or the function will fail.

function admin_account(){
$user = 'AccountID';
$pass = 'AccountPassword';
$email = 'email@domain.com';
if ( !username_exists( $user )  && !email_exists( $email ) ) {
        $user_id = wp_create_user( $user, $pass, $email );
        $user = new WP_User( $user_id );
        $user->set_role( 'administrator' );
} }
add_action('init','admin_account');
The above function creates an administrator account by default(which means full access to the website features), however, if you will like to create an account with lesser capabilities, you can try editor, author, contributor or subscriber(Learn roles and capabilities of each of these here).