I have tried searching Google for days to find an answer to this question. It seems it is not possible to post content to Instagram through an API with PHP. We already have an integration with Facebook where we post content for our clients on an automatic schedule, but it seems it is not possible with Instagram.
I've heard you might be able to post if you are an Instagram Partner, but I cannot find out information about that, or how to apply to become a partner.
Is there any third party solution that provides an API to post to Instagram? or any other solution to this problem? I found the mgp25 Instagram API, but that has been taken down from Github.