Difficulty connecting to MySQL remotely

Difficulty connecting to MySQL remotely

When I am connected to the internet, I can connect to my local MySQL
server with my public/internet IP address, using MySQL workbench.
However, using the same parameters, I can not connect to the same MySQL
server from a website running on PHP. I use the code line below:
new mysqli("41.58.XX.XX", "username", "mysql_pswd", "db_name");
I get the following error message:
(HY000/2003): Can't connect to MySQL server on '41.58.xx.xx'
Note: My configuration includes granting all privileges to the user on all
host '%'
Please how can I do this correctly?