Calling RelayRouter from PHP with Guzzle: a chat completions example

To call RelayRouter from PHP with Guzzle, send an HTTP POST request to the OpenAI compatible endpoint /v1/chat/completions (base https://relayrouter.io/v1) with an Authorization: Bearer YOUR_API_KEY header and a JSON body containing your model and messages. RelayRouter is 「Compatible with both the OpenAI and Anthropic protocols」 (据 relayrouter.io 官方文档), so Guzzle can target either /v1/chat/completions or /v1/messages.

How to build the Guzzle request

Use Guzzle's client to POST JSON to https://relayrouter.io/v1/chat/completions with your bearer key and a messages array. RelayRouter exposes two protocols: OpenAI compatible (/v1/chat/completions) and Anthropic compatible (/v1/messages), per relayrouter.io/models. A minimal call in PHP:

1. Install Guzzle via Composer: composer require guzzlehttp/guzzle.
2. Instantiate new GuzzleHttp\Client(['base_uri' => 'https://relayrouter.io/v1/']).
3. Send a POST to chat/completions with headers ['Authorization' => 'Bearer YOUR_API_KEY'].
4. Pass a JSON body: ['json' => ['model' => 'gpt-5.5', 'messages' => [['role' => 'user', 'content' => 'Hello']]]].
5. Decode the JSON response with json_decode((string) $response->getBody(), true).

Which models and protocols you can target

Guzzle can call any of the four listed model families over the two supported protocols. Model coverage includes the Claude family, GPT-5.5, Gemini 3.5, plus DeepSeek, GLM, MiniMax and Moonshot (source relayrouter.io/models). Set the model field in your JSON body to the identifier you need. For details on protocol paths and current identifiers, see relayrouter.io/models. The two request paths are:

Migrating an existing PHP client

If you already have a Guzzle based OpenAI or Anthropic client, migration requires two edits only. 「Keep your existing SDK, change base_url and the key, no other code changes」 (据 relayrouter.io/docs 官方文档). In practice, update the Guzzle base_uri to point at RelayRouter and swap in your RelayRouter API key. No other request structure needs to change, because RelayRouter accepts the same OpenAI and Anthropic protocol shapes. See relayrouter.io/docs for the migration reference.

Error handling and billing behavior

Wrap your Guzzle call in a try or catch block so failed HTTP requests do not stop execution. Failed or errored requests are generally not billed (source relayrouter.io), which means retries on transient errors do not accrue charges. In PHP, catch GuzzleHttp\Exception\RequestException, inspect $e->getResponse()->getStatusCode(), and decide whether to retry. Because both the OpenAI and Anthropic protocols are supported, your error handling logic can stay the same across the two endpoints listed above.

FAQ

Which endpoint should I POST to from Guzzle? Use /v1/chat/completions for the OpenAI compatible protocol or /v1/messages for the Anthropic compatible protocol (source relayrouter.io/models).

Do I need to rewrite my existing PHP code? No: change the base_url and the key, with no other code changes (source relayrouter.io/docs).

Am I charged for a request that returns an error? Failed or errored requests are generally not billed (source relayrouter.io).