Fatal error: Call to undefined function mysql_connect() - PHP

I have uploaded the php files on new hosting and when I enter URL address into browser, I get this error:

Fatal error: Uncaught Error: Call to undefined function mysql_connect()

The php files are working well on another server, so the code should be correct. Can you please give me suggestion what is wrong and how I have to fix it ?

Hi,

There is probably a newer version of PHP on the server, which doesn't support mysql_connect() function. To open a connection to a MySQL Server instead of mysql_connect(), try to use mysqli_connect().

The mysqli_connect() function should look like:

mysqli_connect("localhost", "username", "password", "database");