Solution to how to open garbled CSV files generated by PHP with UTF-8 encoding

openoffice opens normally but excel opens abnormally. The problem can only be solved after converting the encoding.

Later I found out the reason was that there was no BOM in the output CSV file.

What is BOM?

There is a character called "ZERO WIDTH NO-BREAK SPACE" in UCS encoding, and its encoding is FEFF. FFFE is a character that does not exist in UCS, so it should not appear in actual transmission. The UCS specification recommends that we transmit the characters "ZERO WIDTH NO-BREAK SPACE" before transmitting the byte stream.

In this way, if the receiver receives FEFF, it means that the byte stream is Big-Endian; If FFFE is received, it indicates that the byte stream is Little-Endian. Therefore, the character "ZERO WIDTH NO-BREAK SPACE" is also called BOM. UTF-8 does not require a BOM to indicate the byte order, but can use the BOM to indicate the encoding method. The UTF-8 encoding of the character "ZERO WIDTH NO-BREAK SPACE" is EF BB BF. So if the receiver receives a byte stream starting with EF BB BF, it knows that it is UTF-8 encoded. Windows uses BOM to mark the encoding of text files.

So how to output BOM in PHP?

Before everything is output: print(chr(0xEF).chr(0xBB).chr(0xBF));