How can I connect my website chatbot to the OpenAI API using PHP?

<!-- BEGIN COPY / PASTE -->
    $apiKey = 'your-openai-api-key';
    $url = 'https://api.openai.com/v1/engines/davinci-codex/completions';

    $data = [
        'prompt' => 'Hello, how can I assist you today?',
        'max_tokens' => 150
    ];

    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_HTTPHEADER, [
        'Content-Type: application/json',
        'Authorization: Bearer ' . $apiKey
    ]);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data));

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

    echo $response;
    <!-- END COPY / PASTE -->