I read in Programming PHP (O'Reilly) that flock() "cannot prevent two
PHP scripts running in the same web server process from accessing a
file at the same time".
In my case a single PHP script appends text strings to an existing text
file. Several clients may trigger the same script on the same web page
and thus more than one PHP instance might try to open and append text
to the same file at the same time. I would assume that using flock()
_does_ in fact prevent simultaneous access in this case. Am I correct?
Thanks!

Andrew