I am trying to determine if its possible to export data directly into
an Excel file instead of exporting to a comma-separated (.csv) file
first. And later import that csv-file to an Excel file.
Data is extracted from a MSSQL database. Excel files must be in
either .xls (Excel 97-2003) or .xlsx (Excel 2007) format.

Question 1: Is it possible to create an Excel file from scratch up ?
Question 2: If "yes" to Q1, is it limited to the .xls or .xlsx file
format ?
Question 3: If "yes" to Q1, is there limitations of what information
that can be saved ? (such as formulas, only numbers/text or formating)
Question 4: If "no" to Q1, is there any third-party plug-in or
software that can preform the creation of an Excel file ?

If this is can only be done via some programming then it must be in
PHP (web).