Two notes here:
1) PHP does not need a running copy of filepro to read the datafiles. Just provide it with a directory containing the map file, key file, and the data* file(s) for the table you want to read. Screen files, outfiles, and process files are not used.
2) This function seems to pass back the system error code in brackets [] along with the PHP warning. A list of error codes can be found in your filepro manual's appendix.