Thanks for the invitation and thanks for explaining the concept in detail. The requirements you mentioned are doable. Can you let me know, if you have the source code available for "DataSprings Login module"? If source code is not available, I can still work with a work-around solution.
Following is my proposal for the implementation.
1 - Assuming, we don't have the source code for the "DataSprings Login module", I will be creating a custom desktop module, that will be added to all pages. We can also create a Skin object, if you want.
2 - When this custom module or skin object is loaded, it will create the required cookie - please let me know the details about cookie expiration criteria.
3 - I will create a web-service that will expect the token (created in step# 2) and will return the required JSON array
4 - PHP end will call our end point and get the required informaiton
Please note, I don't know much about PHP, I can provide the support/documentation for the simple end-point, I will be creating but might not be able to code the end-point client in PHP.
Please note, I will be away on weekend, in case you have questions, we can get in touch on Monday. Thanks.