duh, ok. So I did something which had I done ages ago could have save me much heartache.
RFL
'read the freekin logs'
right, so my backup script was nice and easy - permission denied (had I solved my earlier problem of how to echo script erros to the browser, I would have known this straight off!)
the file() or fopen() when a url is involved is still baffling, but someone [hopefully] may know.
the log says:
[Sun Jan 27 17:19:26 2002] [error] (22)Invalid argument: getsockname
[Sun Jan 27 17:19:27 2002] [notice] child pid 412 exit signal Bus error (10)
[Sun Jan 27 17:19:27 2002] [notice] child pid 408 exit signal Bus error (10)
so I read this as apache doesn't understand getsockname (whatever!). I've tried reinstalling the system software, which configures php to base (waytogo Apple - when things screw up, just go and reinstall the system software!). DOes anyone know how to get around this error, or what causes it?