In php 7 documentation i found new and easy methods to connect sql database using functions which start with ingress,like ingress_query(). I would like to know whether it is a good practice to use these functions or should i continue using mysqli_connect() link of documentation is http://php.net/manual/en/function.ingres-fetch-assoc.php
For starters: Ingress is not mySQL, so you cannot use ingress_* functions to connect to mySQL database. Use mysqli or PDO instead.
Also note that:
This extension has been moved to the » PECL repository and is no longer bundled with PHP as of PHP 5.1.0.