If mode is FALSE, the given stream will be
switched to non-blocking mode, and if
TRUE, it will be switched to blocking mode. This
affects calls like fgets() and
fread() that read from the
stream. In non-blocking mode an fgets()
call will always return right away while in blocking mode it
will wait for data to become available on the stream.
This function was previously called as set_socket_blocking() and later
socket_set_blocking() but this usage is
deprecated.
注: Prior to PHP 4.3, this function only worked on socket based streams. Since PHP 4.3, this function works for any stream that supports non-blocking mode (currently, regular files and socket streams).