in reply to Verify FTP Success, prior to deleting files
You can not 100% guarantee that the files are successfully FTP'ed to another system without checking both the source and destination copies of the files.
I can think of a simple solution using the 'PULL' method on the client system. The process flow is as follows:
When a data file becomes available on the FTP server, a cronjob on the server fires off to calculate the CRC of the file and store in the same directory as the data file, with a .crc extension.
At certain fixed interval on the $webserver, a cronjob fires off to FTP get the data file and the .crc of the data file.
The client computes the CRC of the received data file and compares against the CRC calculated on the FTP server. If CRC's match, then the client will FTP delete the data from the FTP server. If CRC's do not match, then report the error or try again.
The sender will never delete data files, only the receiver will delete them after download and CRC comparison.