In addition to the points mentioned in the other answers about the advantages of mysqli:
Prepared Statements support
Support for multiple Statements
Transaction support ( Transactions )
Improved debugging capabilities
Embedded Server Support
It should also be noted that
mysql_ functions no longer receive updates such as fixes and improvements and this is the vital point for you not to use
mysql_ anymore, because in the near future it will no longer exist for new versions of PHP.
In other words, if you continue to
There may be security holes in the
mysql_ functions, two situations can happen with your projects:
mysql_ or bugs API.
mysql_ API is disabled, your scripts will stop working, which will cause you a lot of headaches, as you will have to redo multiple codes.
Note that mysqli means MySQL Improved in Portuguese, would be something like Mysql improved , referring to the API and not to the database system.