Depending on the version of PHP, there are either two or three PHP APIs for accessing the MySQL database. PHP 5 users can choose between the deprecated mysql extension, mysqli, or PDO_MySQL. PHP 7 removes the mysql extension, leaving only the latter two options.
This guide explains the terminology used to describe each API, information about choosing which API to use, and also information to help choose which MySQL library to use with the API.
MySQL deprecated in PHP 5.5.0, and removed in PHP 7.0.0. For a large and old application, this is difficult to search and replace each function.
We can use MySQL functions by creating a wrapper function for each below is running code. <a href="https://www.talkforweb.com.au/php/how-to-use-mysql-in-php-7-version">Click here</a>