I don't mean to discourage the OP, but it is quite involved to integrate STEEM posting into Wordpress. The reasons for
this is that you would need to either require a running `cli_wallet` (where unpractical) or construct **and** sign the
serialized transactions in PHP. I don't know how well ECDSA is implemented in PHP and whether you can easily serialize
transactions, but at least the implementation in python (python-steem is based on python-graphenelib) probably took me a
couple weeks to get it running.

Anyway, [this code](https://github.com/xeroc/python-steemlib/blob/master/steembase/test/test_transactions.py#L11-L38)
shows you how the it's done in python.

If there is a PHP dev willing to develop this, I can offer my help.