Before I invest time and effort, does anyone know any reasons this won't work as a way to create large excel files without hitting the memory limit:
1. Create a spreadsheet as usual, but do not fill in any of the 'standard' rows. By standard, I refer to the bulk content of the spreadsheet. The purpose of this step is to get the xlsx component files (eg rels, app.xml, core.xml, etc) all ready for use.
2. Write to disk in a temp file
3. Open xl/worksheets/sheet1.xml with ordinary file manip functions (eg fopen)
4. Cut and save the closing portion of this file, leaving sheet1.xml with EOF exactly at the right place for appending rows.
5. Manually append the bulk rows, writing as you go, so that this file is never loaded into memory. Requires knowledge of the format, but this is easily obtained through a little study of examples you can make.
4. Replace the ending portion that was taken out in step 4
Can anything think of a reason this won't work?