Recommended minimum PHP Version Revision to 5.4.0

[cpiggott]

I've been looking through the DwollaSwagger API and noticed that there are inconsistencies within the minimum version for PHP and code syntax that is used.

Specifically a few issues I've found are:

Short Array Syntax : This can be seen throughout the application, creating arrays using short syntax example:
[1,2,3,4]
This was not supported until version 5.4.0 of PHP, but is seen throughout the application. PHP 5.4.0 New Features, Short Array Syntax

Function Array Dereferencing : Dereferencing a function array return was not supported until 5.4.0 either but can be seen at in ApiClient:L307 and in other places in the app.
Ex:

$data = !isset(self::http_parse_headers($http_header)["Location"])

PHP 5.4.0 New Features, Function Array Dereferencing