Express agency, implied agency

Art. 1869. Agency may be express, or implied from the acts of the principal, from his silence or lack of action, or his failure to repudiate the agency, knowing that another person is acting on his behalf without authority.

Agency may be oral, unless the law requires a specific form.

Art. 1870. Acceptance by the agent may also be express, or implied from his acts which carry out the agency, or from his silence or inaction according to the circumstances. (Civil Code of the Philippines)

Acceptance, silence, failure to repudiate, inaction or action by the agent or the principal may result in agency.