PHP Warning: Missing argument 2 for Mailchimp::call() - php

Question

Can be found there many resources on Internet with the same code and instructions about how to show your MailChimp subscriber count in WordPress. I used that code without problems until today, when received an PHP Warning:
PHP Warning: Missing argument 2 for Mailchimp::call(), called in
/.../mc-subscriber-count/mc-subscriber-count.php on line 19 and
defined in /.../mc-subscriber-count/Mailchimp.php on line 192
The mc-subscriber-count.php full code:
function wpb_mc_sub_count() {
include "Mailchimp.php";
$lastRunLog = __DIR__ . '/logs/lastrun.log';
$subfile = __DIR__ . '/logs/subcount.log';
$lastRun = file_get_contents( $lastRunLog );
if ( time() - $lastRun >= 86400 ) {
$MailChimp = new MailChimp( 'Your_MailChimp_API_Key' );
$mc = $MailChimp->call( 'lists/list' ); // THE LINE 19
/*****************************************************/
$subscriber_count .= $mc[data][0][stats][member_count];
file_put_contents( $lastRunLog, time() );
file_put_contents( $subfile, $subscriber_count );
} else {
$subscriber_count .= file_get_contents( $subfile );
}
return number_format( $subscriber_count );
}
add_shortcode( 'mc-subscribers', 'wpb_mc_sub_count' );
add_filter( 'widget_text', 'do_shortcode' );
The Mailchimp.php code (only the function from the line 192 - full code here):
public function call($url, $params) {
$params['apikey'] = $this->apikey;
$params = json_encode($params);
$ch = $this->ch;
curl_setopt($ch, CURLOPT_URL, $this->root . $url . '.json');
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
curl_setopt($ch, CURLOPT_POSTFIELDS, $params);
curl_setopt($ch, CURLOPT_VERBOSE, $this->debug);
$start = microtime(true);
$this->log('Call to ' . $this->root . $url . '.json: ' . $params);
if($this->debug) {
$curl_buffer = fopen('php://memory', 'w+');
curl_setopt($ch, CURLOPT_STDERR, $curl_buffer);
}
$response_body = curl_exec($ch);
$info = curl_getinfo($ch);
$time = microtime(true) - $start;
if($this->debug) {
rewind($curl_buffer);
$this->log(stream_get_contents($curl_buffer));
fclose($curl_buffer);
}
$this->log('Completed in ' . number_format($time * 1000, 2) . 'ms');
$this->log('Got response: ' . $response_body);
if(curl_error($ch)) {
throw new Mailchimp_HttpError("API call to $url failed: " . curl_error($ch));
}
$result = json_decode($response_body, true);
if(floor($info['http_code'] / 100) >= 4) {
throw $this->castError($result);
}
return $result;
}
How to solve that warning?
UPDATE
I forgot to mention that I see that there is missing a second argument, but I don't understand what this second argument can be.
P.S. I am not a PHP coder, so don't beat me.

Answer 1

After the received comments I analysed repeatedly the above two functions and decided to add as a second parameter to the line 19 the `$params` variable, so it looks now like this:
$mc = $MailChimp->call( 'lists/list', $params );
I don't know if this is the correct way, but I will wait now for errors, if will be some there.
UPDATE
Because I received here only downvotes instead of help (but it doesn't matter) and my first solution doesn't worked (see the deleted text), I googled again and finally I found a better one (I hope) to display the MailChimp subscribers count in Wordpress. I just wrapped the recommended code in a shortcode like this:
function wpb_mc_sub_count() {
$api['key']= 'INSERT-YOUR-API-KEY-HERE';
$url='https://INSERT-YOUR-US-DOMAIN-KEY.api.mailchimp.com/3.0//lists/INSERT-YOUR-LISTID-HERE/?apikey=INSERT-YOUR-API-KEY-HERE';
$lastRunLog = '/logs/lastrun.log';
$subfile = '/logs/subcount.log';
$lastRun = file_get_contents($lastRunLog);
if (time() - $lastRun >= 3600) {
// it's been more than one hour so we will connect to the API
$ch = curl_init();
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_URL,$url);
$result=curl_exec($ch);
curl_close($ch);
$json = json_decode($result, true);
$total= $json['stats']['member_count'];
// update lastrun.log with current time
file_put_contents($lastRunLog, time());
file_put_contents($subfile, $total);
} else {
$total = file_get_contents($subfile);
}
//echo $total;
return $total;
}
add_shortcode( 'mc-subscribers', 'wpb_mc_sub_count' );
//add_filter( 'widget_text', 'do_shortcode' );
Just put the [mc-subscribers] shortcode where you want to display your MailChimp subscribers count.