batch change encoding to UTF-8 for several text (php) files

You can use recode
recode UTF-8 *.php -v

provided that all the files have the same encoding.
Otherwise you can try with something like
iconv -f US-ASCII -t UTF-8 *.php

a minor problem

It could be an apparent problem if there aren’t non-ascii characters in a file: then these files are yet recognized, with
file -i --mime-encoding *
as us-ascii.
So you can add a non ascii character, like è:
sed -i -e “$aè” *.php

and afterwards redo the command “recode” as above and replace some ascii expression, like agrave; with UFT-8 à character.
Eventually you will delete the “è” from the end of the files.

How to change encodig of “.srt” Subtitle File in UTF-8

To encode your SRT file in UTF-8 (for instance: “”), please follow this process:

1. Rename (F2) the “” file with your PC in “”.
2. Launch a text app, like Kate.
3. Click on the “File” menu then select “Save the file as…”.
4. In coding option, select “UTF-8”. Then save your file.
5. Rename (F2) the file “” to “”.

from: Zappiti Player 4K [EN]