dirname --- fix documentation in Italian

[davide75]

From manual page: https://php.net/function.dirname
If I display the page in italian language there is no documentation about second parameter of the function ($level). Compare the two screenshots to see more

[DavidePastore]

Hi @davide75. Thanks for reporting this issue! Feel free to take a look at the repository and sync the content with the English version of the documentation, by creating a new pull request.