As per our New Civil Code, verbal contracts are considered binding as to the two parties who made it. However, it will be a battle of evidences in case there will be questions as to the existence of a verbal contract if court proceedings will push through.
The best way to deal with such is to talk to the ones who interviewed you and honestly say your reasons for declining the job offer. It would be harder to decline if there was already a written employment contract in play, but since all negotiations were made verbally, it can still be talked over with them. Hopefully, there will be no power-tripping and intimidating gestures by the employer during your conversations with them.
It is also well within your right to ask for an employment contract in case you still want to push through with the job offer, para at least clear yung scope of responsibility mo for your new job and the salary that you are entitled to receive per month. In case pumayag yung employer mo, make sure to read all the provisions of the employment contract and ask for clarification for any unclear parts para pulido yung contract na gagawin. Most importantly, ask for a copy of your employment contract for future basis and don't forget to ask for the company handbook regarding its rules and regulations.
In case di sila magbigay ng employment contract, ask for the reason as to why di nila magawa yun and then tingnan mo kung justified naman ang rationale nila. There are some fledgling companies that do not have the required resources yet sa HR para gumawa ng mga employment contracts, kaya some opt to give you the contract after nagtatrabaho ka na. Pero dapat clear yun and hingi ka rin ng documentary evidence na dapat to follow yung employment contract mo and dapat din may karapatan ka pa rin na magclarify and magdispute ng terms and conditions ng contract since late mo natanggap yung contract...
Take everything I say with a grain of salt, since law student pa lang ako. It is always better to ask a real lawyer for his legal opinion regarding your situation. Nevertheless, I wish you good luck in your situation, and may it be resolved with both parties not being aggrieved in the end...