I have no luck finding if I can create an editable form with FPDF. Is it possible? I would like to create a table with editable cells and be able to save it with changes.
If by being "able to save it with changes" you mean being able to do so in acrobat reader, you are out of luck.
A pdf with such a property is called "reader enabled". Reader enabling a pdf includes adding a special electronic signature to it (a "usage right" signature) with a private key held by adobe. Thus, only adobe software (e.g. Adobe acrobat) can reader enable a pdf.