Create a dynamic database for each user using PHP

Any suggestions on how we can create dynamic database for each user using PHP (as an when they register)? I am using the below code - it works on the local server, but not working in the live server on digitalocean. Is this a permission issue to create DB?

public function setupNewDatabaseWithSubdomainName($domain_name = '') {
        $db2 = array(
            'dsn' => '', 'hostname' => $this->hostname, 'username' => $this->username, 'password' => $this->password, 'database' => $domain_name,
            'dbdriver' => 'mysqli', 'dbprefix' => '', 'pconnect' => FALSE, 'db_debug' => (ENVIRONMENT !== 'production'),
            'cache_on' => FALSE, 'cachedir' => '', 'char_set' => 'utf8', 'dbcollat' => 'utf8_general_ci', 'swap_pre' => '',
            'encrypt' => FALSE, 'compress' => FALSE, 'stricton' => FALSE, 'failover' => array(), 'save_queries' => TRUE
        );

        $sql_db = "CREATE DATABASE IF NOT EXISTS " . $domain_name;
        $this->db->query($sql_db);
        print_r($this->db->error());
        $this->dbNew = $this->load->database($db2, TRUE);
        $arr_table_lists = $this->retun_all_tables_from_database($this->db->database);
        foreach ($arr_table_lists as $tbl_name) {
            $sql_new = "";
            $sql_new = "SHOW CREATE TABLE " . $this->db->database . "." . $tbl_name->table_name;
            $query = $this->db->query($sql_new);
            $result = $query->result_array();
            $sql_new = strtolower($result[0]['Create Table']);
            $sql_new = str_replace("create table", "create table if not exists ", $sql_new);
            $this->dbNew->query($sql_new);
        }
    }