Mailchimp API发送自定义字段

I am trying to send the custom field to mailchimp but not sure how to do this.

If you see below, I am trying to send company information to one of my Audiences but it's not sending through.

Here is the pasted code as well:

 // member information
    $json = json_encode([
        'email_address' => $user_row['email'],
        'status'        => 'subscribed',
        'COMPANY'       =>  $company_info['name'],
        'merge_fields'  => [
            'FNAME'     => $user_row['first_name'],
            'LNAME'     => $user_row['last_name']
        ]
    ]);

I have created the custom field inside the mailchimp under targeted audiences. As you can see here:

So anyone can please help me that what I am doing wrong that company information is not syncing.

On Audiences I am receiving blank company name.

 'COMPANY'       =>  $company_info['name'],

The above line should be inside the 'merge_fields' like this

$json = json_encode([
    'email_address' => $user_row['email'],
    'status'        => 'subscribed',
    'merge_fields'  => [
        'FNAME'     => $user_row['first_name'],
        'LNAME'     => $user_row['last_name'],
        'COMPANY'   => $company_info['name']
    ]
]);