Make a text field data as uppercase

Replies: 0

Is there any way to make a text field of a form be stored as uppercase in the submissions?

I saw the related post but I’m not fully understand to install the PHP code. After I create the mu-plugins directory, what is the .PHP file name? I can name it randomly? Or there is a specific name for the .PHP file. And, is the PHP code still works on latest version of the plugin?

Thanks in advance!