phplot.php: type casts for PHP 8.2

[jeriba4]

As announced in issue comment, I´ve just cast the arguments of the calls used for my use cases to int, which fixes PHP 8.2 type mismatch notifications.

Of course, a more profound approach would be to type the respective function parameters or class properties to int or, if anyway needed, nullable int (?int), but that might break backward compatibility with PHP 7.x.

[mostafasoufi]

👍🏽