How does an API typically use HTTP status codes to communicate the result of a request, and what do common codes like 200, 404, and 500 represent?

HTTP status codes provide a standardized way for an API to communicate the outcome of a request, with codes in the 200 range indicating success, such as 200 for a successful GET request or 201 specifically for a successful resource creation, codes in the 400 range indicating a client error, such as 404 for a resource that does not exist or 400 for a malformed request, and codes in the 500 range indicating a server side error, giving API consumers a reliable, consistent way to programmatically determine what happened without needing to parse the response body just to know if something succeeded or failed.

http_response_code(404);
echo json_encode(['error' => 'Product not found']);