If you invited a friend of an acquaintance, we would like to know, if the applicant is really the person invited. An existing friendship / acquaintance is in general not difficult to prove.
Evidence can for example be given through the following ways:
Xerox copies of the passport of the host. If he/she has visited you: with stamps of the Philippine border control
Joint hotel bookings, at least two visits or holidays together in order to prove the seriousness of the relationship. This applies also for holidays / residences together in other countries.
Flight tickets / Boarding cards.
Evidence of telephone connections or print-outs of VoIP connections such as “skype”.
Correspondence by post or by email (we do not wish to read your letter, but a a brief look can demonstrate a regular correspondence between friends / acquaintances. All your statements will be treated confidentially. Because of the private nature of these documents we leave it completely up to your decision to submit these documents. The Embassy also receives screenshots of incoming post or VoIP-connections).
Pictures are not accepted by the Embassy as only evidence of acquaintance, as they can hardly represent a relationship between host and guest.