mailgun/mailgun-php — pull request #57 by jchamberlain (2014-09-08 19:16:01+00:00)
Title: Allow any data type for custom data

Since a "v:custom-name" header can have any JSON-encoded value and can be used multiple times, `MessageBuilder::addCustomData()` shouldn't require an array. I've tested, and bypassing the message builder to manually pass in non-array variables works just fine.

See http://documentation.mailgun.com/user_manual.html#attaching-data-to-messages