The Instagram API can be used with PHP to display real-time content, such as user feeds or hashtags, on a website. To get started, developers must register for an access token and obtain an API key, which requires logging onto their personal Instagram account. The API uses HTTP requests to communicate with the Instagram server, and endpoints are typically named after the functionality they provide. Developers can use built-in PHP functions such as `json_encode()` and `json_decode()` to handle JSON responses from the API. To integrate Instagram content into a PHP application, developers can use APIs like Hashtagy, which provides an endpoint for generating hashtags associated with a keyword. The review process for using the Instagram API is strict, requiring developers to submit a compelling case of why sandbox mode is not sufficient for their needs while illustrating how it meets the requirements defined by Instagram. Sandbox mode allows developers to display up to 20 posts associated with a particular user ID without needing further laborious development. However, if the use case requires more functionality, developers must formally engage with Instagram and be met with a higher chance of success.