cURL with API URL and result URL in PHP?

I want to use an API with cURL in PHP, but I don't know how to call one URL for sending, and one URL for receiving data. I want to convert images to webp, I send jpeg, jpg, png pictures to the API, and I want to download the webp version of it.

This is the API URL: https://api.webp.to/v1/convert/ And this is the result URL: https://api.webp.to/v1/results/

I wrote this code:

    $picture="picture.jpg";
    $fp = fopen("picture.webp", "w+");
    $data = array(
        'lang' => 'en',
        'convert_to' => 'jpg-webp',
        'ocr' => false,
        'file_contents' => curl_file_create($picture)
    );
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_URL, "https://api.webp.to/v1/convert/");
    curl_setopt($curl, CURLOPT_HTTPHEADER, array(
        "Authorization: <API_KEY_INSERTED_HERE>" 
    ));
    curl_setopt($curl, CURLOPT_POST, 1);
    curl_setopt($curl, CURLOPT_POSTFIELDS, $data);
    curl_setopt($curl, CURLOPT_FILE, $fp);
    curl_setopt($curl, CURLOPT_FOLLOWLOCATION, true);
    curl_setopt($curl, CURLOPT_TIMEOUT, 0);
    curl_exec($curl);

I need to insert somewehere a result URL, because it is different from API URL. I tried to get redirect info rom the curl_exec, but there is no redirect in the returning data.

Here is the API which I use: https://webp.to/api

They provide only Python code:

import requests
import time
import shutil
import json
headers = {'Authorization': 'f134382194a844c8bb589af58ef283e9'}
file_list = ['testfiles/blah.webp', 'testfiles/blah.webp', 'testfiles/blah.webp']
params = {
    'lang': 'en',
    'convert_to': 'webp-docx',
    'ocr': False
}
api_url = 'https://api.webp.to/v1/convert/'
results_url = 'https://api.webp.to/v1/results/'

def download_file(url, local_filename):
    with requests.get("https://api.webp.to/%s" % url, stream=True) as r:
        with open(local_filename, 'wb') as f:
            shutil.copyfileobj(r.raw, f)
    return local_filename

def convert_files(api_url, params, headers):
    files = [eval(f'("files", open("{file}", "rb"))') for file in file_list]
    print(files)
    r = requests.post(
        url=api_url,
        files=files,
        data=params,
        headers=headers
    )
    return r.json()

def get_results(params):
    if params.get('error'):
        return params.get('error')
    r = requests.post(
        url=results_url,
        data=params
    )
    data = r.json()
    finished = data.get('finished')
    while not finished:
        if int(data.get('queue_count')) > 0:
            print('queue: %s' % data.get('queue_count'))
        time.sleep(5)
        results = get_results(params)
        print(results)
        results = json.dumps(results)
        if results:
            break
    if finished:
        print(data.get('files'))
        for f in data.get('files'):
            print(f.get('url'))
            download_file("%s" % f.get('url'), "%s" % f.get('filename'))
        return {"finished": "files downloaded"}
    return r.json()

get_results(convert_files(api_url, params, headers))

Thank you for help!