The name is usually spelled SOMMER in Alsace. I have about 35 Sommer in my database, which currently totals 63000+. Most of them are Catholics, from Gundershoffen and nearby towns.
I'm assuming this Sommer, though, was Lutheran, since he married Ruch. She is presumably Marguerite Ruch, b 2 Apr 1813 at Ernolsheim-les-Saverne, daughter of Jean Adam Ruch (1785-1845) and Maria Salome Gunseth (1782-1848), from Ernolsheim. They emigrated to America and both of them died in Allen Co, IN.
The name is not particularly common in Alsace and seems mostly to be found among Catholics. There are a couple of Philippe Sommer at Nehwiller, though I don't see any unaccounted-for who might match yours, and the names of the families into whom they marry are just not familiar to me; this Sommer family may well be Catholic, but I'm not deeply versed in Nehwiller, other than the Ruchs I have tracked down there.
Two or three miles southeast is Goersdorf, where there are at least 2 Sommer families in the 19th century, who came there from Wintzenbach, over in the Rhine plain, but originate at Oberbetschdorf. The patriarch of the family was Phililppe Frederic Sommer, c1750s-1830s, and you would think the name might be perpetuated in that line, other than just his son, but I'm not seeing them. The Sommer at Goersdorf are intermarried to Gundershoffen (on the Lutheran side) and to Niedermodern (also on the Lutheran side), so I take them to be protestant. (The French records, pre-1872, do not give religious affiliation, though they do after 1921, when Alsace and Lorraine returned to France. During the German occupation, 1872-1918, the religion is usually stated in records.)
You can see pedigrees of the Nehwiller Sommer at www.geneanet.org
(you have to register, but use of the site is free, as far as the family trees, the most valuable info on it), and also some shorter trees of the Oberbetschdorf/Wintzenbach group. The 1890-1992 birth record data at www.geopatronyme.com
gives locations for Sommer births in that period -- the name is most commonly found in Bas-Rhin), though most of them are references to Catholic towns, and anyway, it's almost 100 years later than your Philippe.
I still have a couple of ideas and will try to work on them tomorrow, if I don't have any interruptions.