php - mysql query inserting data multiple times

I have a table log_Data where i log searched keyword that user enter. I am facing an issue that mysql query is inserting data multiple time. query is super simple INSERT INTO TABLE_NAME (id, keyword, date_adde) ... but if user enter some word... the query will insert it and after some seconds it will insert again and sometimes it insert same record for 4 5 times.

How can i limit and make this insertion more accurate so i can avoid duplication and get better and more accurate search reports.

EDIT

inside my controller i have:

        if(isset($this->request->get['search']) && $this->request->get['search'] != ' '){
            $search_log = array(
                'keyword' => $this->request->get['search'],
                'source'  => '0', //0 for website and 1 for application
                'total_result' => $product_total
            );
            $this->model_catalog_product->searchLog($search_log);
        }

Inside my Model i have:

public function searchLog($data){
    $query = $this->db->query("INSERT INTO search_log SET keyword = '" . $this->db->escape($data['keyword']) . "', record = '" . (int)$data['total_result'] . "', customer_id = '" . (int)$this->customer->getId() . "', source = '" . (int)$data['source'] . "', ip = '" . $this->db->escape($this->request->server['REMOTE_ADDR']) . "', date_added = NOW()");
}

attached an image where a customer searched for heel 'highlighted with black' is inserted 7 times with difference in few seconds... the customer originally searched for 1 time only... same as for other words as well...

Solution:

first, check your code. Secound make a unquiq key: