应用程序中的数据库连接

I am developing a application that is in php and PostgreSQL.

What I want to know is which of these is best?

1. I should create connection every time i have to make a query like using pg_connect and close it after the query operations
2. Or should i start the connection first time at the initial launch

Please guide me the correct way to achieve my objective.

Connect at the start of your script, close it at ending. No need to re-connect on each query.