How to seperate hydrogen and oxygen in/after electrolysis?

I took my small solar panel and stuck the wire end in an upside down soda bottle in a bucket full of water. The hydrogen and oxygen both bubbled up into the bottle and turned back into water immediately with no explosion or fire or heat. They have to be collected in separate containers or you will get nothing. Compress either and nothing should go wrong if you don't allow anything else to mix with them; oxygen doesn't burn (but will make any impurities that mix in with it burn explosively) and hydrogen can't burn without the presence of oxygen.