If mode is 0, the given stream will be switched to non-blocking mode, and if 1, 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.
TRUE on success or
FALSE on failure.
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).
See also stream_select().