Besides, except and apart from sometimes made confusion and question where to use or how to use.
Besides usually make additional point to something.
Example
Besides Rock and Roll music, I also like Punk Rock music.
Besides PHP, we have to learn HTML and CSS.
Except is used when something need to be prevent from being included.
Example
He can play all musical instruments except the quitar.
Apart from on the other hand, can be used in both senses.
Apart from Rock and Roll music, I also like Punk Rock music.
He can play all musical instruments apart from the quitar.