如何结合ChatGPT PHP实现在线客服功能？

$api_key = 'your-api-key';
$model = 'gpt-3.5-turbo';

$message = '你好，我有一个问题。';
$response = chat_with_gpt($message, $api_key, $model);

$reply = $response['choices'][0]['message']['content'];
echo "回复：$reply";

function chat_with_gpt($message, $api_key, $model) {
    $url = 'https://api.openai.com/v1/chat/completions';
    $data = [
        'messages' => [
            [
                'role' => 'user',
                'content' => $message,
            ],
        ],
    ];

    $headers = [
        'Content-Type: application/json',
        'Authorization: Bearer ' . $api_key,
    ];

    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
    curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data));

    $response = curl_exec($ch);
    curl_close($ch);

    return json_decode($response, true);
}