Jamieson, Fausset and Brown on Revelation 11:19

19. A similar solemn conclusion to that of the seventh seal, Re 8:5, and to that of the seventh vial, Re 16:18. Thus, it appears, the seven seals, the seven trumpets, and the seven vials, are not consecutive, but parallel, and ending in the same consummation. They present the unfolding of God's plans for bringing about the grand end under three different aspects, mutually complementing each other.

the temple--the sanctuary or Holy place (Greek, "naos"), not the whole temple (Greek, "hieron").

opened in heaven--A and C read the article, "the temple of God "which is" in heaven, was opened."

the ark of his testament--or "... His covenant." As in the first verse the earthly sanctuary was measured, so here its heavenly antitype is laid open, and the antitype above to the ark of the covenant in the Holiest Place below is seen, the pledge of God's faithfulness to His covenant in saving His people and punishing their and His enemies. Thus this forms a fit close to the series of trumpet judgments and an introduction to the episode (the twelfth and thirteen chapters) as to His faithfulness to His Church. Here first His secret place, the heavenly sanctuary, is opened for the assurance of His people; and thence proceed His judgments in their behalf (Re 14:15, 17; 15:5; 16:17), which the great company in heaven laud as "true and righteous." This then is parallel to the scene at the heavenly altar, at the close of the seals and opening of the trumpets (Re 8:3), and at the close of the episode (the twelfth through fifteenth chapters) and opening of the vials (Re 15:7, 8). See on Re 12:1, note at the opening of the chapter.