By Rabbi Berach Steinfeld
The Rema 695 says there is a mitzvah to be marbeh in seudas Purim. Any meal a person eats on Purim that is lichvod Purim is included in the above mentioned mitzvah. Nevertheless, one meal is the minimum. The minhag is to be mekayem the mitzvah after M
The Magen Avraham 695:9 says there is no requirement to eat bread. The Aruch Hashulchan argues and says bread is required.
If a person threw up his entire meal, he is not yotzei based on Ksav Sofer 96 and Kaf Hachaim 273:7, therefore, if the above happens he needs to eat again.
One is not allowed to be kovea a seuda he usually does not eat on Erev Shabbos as we find in 249:2. The exception will be if he has a seudas mitzvah based on Rema 249. When Purim falls out on Friday, one should make the seuda earlier, before chatzos, as we find in the Rema 695:2. Reb Shlomo Zalman in Halichos Shlomo 19:81 says one should not be mekabel Shabbos early because it is not recognizable that the seuda is eaten for Purim. In the Sefer Purim Shechol BeShabbos brings an opinion to start seudas Purim during the day, then spread a tablecloth and make Kiddush once it turns into nightfall.
In the event one ate the Purim meal and then was pores mapa and made Kiddush, during Birchas Hamazon he would say retzeh and not say Al Hanisim. If he says both these tefillos it would render a tarti desasri. Therefore, in order not to have sfeikos, you are best off eating on Friday morning and making a new Shabbos meal on Friday night with no sfeikos.
May we be zocheh to be mekayem seudas Purim and Se
{Matzav.com}
… Mishna Berura 1 adds that there is also a mitzvah to eat after nightfall….
To clarify:
After nightfall meaning the night BEFORE the day of Purim (just like the Megillah which is read by night and by day) Not the night after Purim (night before Shushan Purim), which many people extend the Seudah into that night – which is OK if most of the Seudah is consumed during Purim day.