For example, folder a contains 1.csv, 2.csv, and 3.csv, and folder b contains 2.csv, 3.csv, and 4.csv. The csv formats in folders a and b are the same.
How can I use php to combine folders a and b into a new folder c, and merge csv files with the same names of a and b.
Expected results: There are 1.csv, 2.csv, 3.csv, 4.csv in the c folder, including 2. The contents in csv and 3.csv are the merged contents of 2 and 3 in folders a and b.