The document discusses handling multibyte CSV files in PHP. It explains that the fgetcsv() function can parse CSV files but does not support multibyte encodings by itself. However, setting the locale to match the CSV file's encoding using the setlocale() function allows fgetcsv() to properly parse multibyte CSV files. The document demonstrates using setlocale() to parse a CSV file encoded in EUC-JP by setting the locale to "ja_JP.eucJP", which successfully reads the multibyte data.