I was not aware of PDO or MYSQLi functions before developing the project in PHP (Version 5.5) and MYSQL.

But now the project is almost completed but yet to launch the software.

If I launch the project, what problems will I face?

Please help me out. Thanks in advance.

If I launch the project, what problems will I face?

Technically none yet. At some point in the future if you decide to upgrade to a newer PHP version, your code will stop working.

http://php.net/manual/en/mysqlinfo.api.choosing.php

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