"Art 1324 is modified by Art. 1479"
(Meaning the former is the general rule while the latter is an exception)
Atkins, Kroll and Co., Inc. V. B. Cua Hian Tek (L-9871, Jan. 31, 1958)
"If the option is given without a consideration, it is a mere offer of a contract of sale, which is not binding until accepted."
(Abandoning the ruling in the Southwestern Sugar and Molasses Co.)
Finally, in the case of Sanchez v. Rigos (45 SCRA 368) the court abandons the ruling in Southwestern Sugar and Molasses Co. and affirms Atkins, Kroll and Company.
(PS: I've heard that there is an en banc case affirming Atkins, Kroll and Company. i'll post the citation here when I find it.)