yes, you need a China visa to go to Beijing. Hong Kong applies different exit & enter controls from Mainland China, Philippines passport holders don't need a visa to Hong Kong for 14 days at most, however, they need a visa to enter Mainland China.

thanks for the information... how can we apply for a visa in beijing china? and how long will they give us before it will expire? because we are planning to go there on october, is it advisable that we apply visa as early as now or apply on september? and how much will it cost us?

You can apply for China tourist visa (L visa)at China Embassy/Consulate in Philippines according to the consular districts. Generally speaking, the single-entry tourist visa (L visa) is valid for 3 months, you can apply for China visa in August or september, if you apply for it too early, it expires before you use it to enter China. It costs 1400 pesos per passport for Filipino applicant.