Create a contact and an associated contribution in CiviCRM using APIv4

Steps

1. Set up authentication appropriate to your access method — REST calls need a site key + API key (or the newer AuthX bearer-token flow), while in-process calls (PHP extensions) use civicrm_api4() directly
2. Call Contact::create with contact_type and core fields (e.g. display_name) to create the donor's contact record, or Contact::get first to check for an existing match
3. Use APIv4 chaining to nest a Contribution::create call inside the Contact::create call, referencing the newly created contact via the back-reference syntax ('$id')
4. In the chained Contribution::create, set financial_type_id (e.g. Donation), total_amount, receive_date, and contact_id (populated automatically via the chain)
5. Execute the chained call and inspect both the top-level Contact result and the nested chain result for the created Contribution ID
6. For high-volume inserts, prefer Explicit/Implicit Joins or the Order/Payment APIs over per-record chaining, since chained calls execute once per outer result and can be slow at scale