Hi just a quick tip for us noobies.
If you get this error,
htmlspecialchars(): Invalid multibyte sequence in argument
There are 3 things that helped me.
Make sure you file is saved in UTF-8 most decent editors will give you this option.
Make sure your Database table is saved UTF-8 as well.
Finally and this is where i tripped myself up for a day is trying to display the field in a view so remove the field from the View attributes and the page will render correctly for you. To display the file you need to follow this tutorial.
Inserting a Blob into a database.
Just something that might help someone else.