PHP MySQL Insert record if not exists in table

In this video you can find how to use php mysql insert query for checking data already inserted or not. I have use insert query with sub query with where condition and not exits. I have simple use inner join in this insert query for checking data already inserted or not. Source Code - http://www.webslesson.info/2016/05/php-mysql-insert-record-if-not-exists-in-table.html