Not sure what is going on but composer isn't happy with the composer.json file. It is currently:

{
"name": "authorizenet/authorizenet",
"type": "library",
"description": "Official PHP SDK for Authorize.Net",
"keywords": ["authorizenet", "authorize.net", "payment", "ecommerce"],
"license": "proprietary",
"homepage": "http://developer.authorize.net",
"require": {
"php": ">=5.6",
"ext-curl": "*",
"ext-json": "*",
"ext-simplexml": "*",
"ext-xmlwriter": "*",
"goetas-webservices/xsd2php-runtime":"^0.2.2",
"authorizenet/authorizenet": "~1.9"
},
"require-dev": {
"phpunit/phpunit": "~4.0",
"phpmd/phpmd": "~2.0"
},
"autoload": {
"classmap": ["lib"]
},
"autoload-dev": {
"classmap": ["tests"]
}
}

Error message is:

Your requirements could not be resolved to an installable set of packages.

Problem 1
- The requested package authorizenet/authorizenet No version set (parsed as 1.0.0) is satisfiable by authorizenet/authorizenet[No version set (parsed as 1.0.0)] but these conflict with your requirements or minimum-stability.

Any suggestions would be greatly appreciated.

Thanks,

Al