Error when sending large chunks of data over a secure TLS connection with older PHP versions

[clue]

Originally reported here: reactphp/stream#64

This can actually easily be reproduced by sending a "large" chunk of data at once over a TLS connection. On my system, this appears to be anything larger than around 30 KB at once passed to the underlying fwrite() call.

error:1409F07F:SSL routines:SSL3_WRITE_PENDING:bad write retry

This is actually a bug in PHP that has been reported via https://bugs.php.net/bug.php?id=72333. The bug has been present for years and has been fixed recently via php/php-src@17e9fc9 which landed in 7.1.4 and 7.0.18.

I've played around with different buffers and write chunks and it looks like this can be worked around by limiting the write chunk size to anything smaller than around 8 KB.

[clue]

Note that this has only been fixed recently in 7.1.4 and 7.0.18, which means there are plenty of versions that are still affected by this issue. As such, I believe it makes sense to provide a work around for affected versions here.

The work around requires limiting the maximum chunk size to write at once. This feature PR is currently outstanding here: reactphp/stream#105