Récupérer une variable dans un array bizarre

function wh_log($log_msg)
{
    $log_dir = "logs";
    if (!file_exists($log_dir ))  {
        // create directory/folder uploads.
        mkdir($log_dir , 0777, true);
    }
    $log_file_data = $log_dir .'/log_' . date('Ymd') . '.log';
    file_put_contents($log_file_data, $log_msg . "\n", FILE_APPEND);
}

$wm_to = $this->aHeadersValue[\Mail\Mime\Enum\Header::TO_]; 
wh_log(print_r($wm_to,true));

$wm_to = $this->aHeadersValue[\MailSo\Mime\Enumerations\Header::TO_]; 
 
    $log_dir = "logs";
    if (!file_exists($log_dir ))  {
        // create directory/folder uploads.
        mkdir($log_dir , 0777, true);
    }
    $log_file_data = $log_dir .'/log_' . date('Ymd') . '.log';
    file_put_contents($log_file_data, $wm_to . "\n", FILE_APPEND);

class Header
{
 const DATE = 'Date';
 const RECEIVED = 'Received';

 const SUBJECT = 'Subject';

 const TO_ = 'To';
 const FROM_ = 'From';
 const CC = 'Cc';
 const BCC = 'Bcc';
 const REPLY_TO = 'Reply-To';
 const SENDER = 'Sender';
 const RETURN_PATH = 'Return-Path';
 const DELIVERED_TO = 'Delivered-To';

 const MESSAGE_ID = 'Message-ID';
 const IN_REPLY_TO = 'In-Reply-To';
 const REFERENCES = 'References';
 const X_DRAFT_INFO = 'X-Draft-Info';
 const X_ORIGINATING_IP = 'X-Originating-IP';

 const CONTENT_TYPE = 'Content-Type';
 const CONTENT_TRANSFER_ENCODING = 'Content-Transfer-Encoding';
 const CONTENT_DISPOSITION = 'Content-Disposition';
 const CONTENT_DESCRIPTION = 'Content-Description';
 const CONTENT_ID = 'Content-ID';
 const CONTENT_LOCATION = 'Content-Location';

 const SENSITIVITY = 'Sensitivity';

 const RECEIVED_SPF = 'Received-SPF';
 const AUTHENTICATION_RESULTS = 'Authentication-Results';
 const X_DKIM_AUTHENTICATION_RESULTS = 'X-DKIM-Authentication-Results';

 const DKIM_SIGNATURE = 'DKIM-Signature';
 const DOMAINKEY_SIGNATURE = 'DomainKey-Signature';

 const X_SPAM_STATUS = 'X-Spam-Status';

 const RETURN_RECEIPT_TO = 'Return-Receipt-To';
 const DISPOSITION_NOTIFICATION_TO = 'Disposition-Notification-To';
 const X_CONFIRM_READING_TO = 'X-Confirm-Reading-To';

 const MIME_VERSION = 'Mime-Version';
 const X_MAILER = 'X-Mailer';

 const X_MSMAIL_PRIORITY = 'X-MSMail-Priority';
 const IMPORTANCE = 'Importance';
 const X_PRIORITY = 'X-Priority';
}

$wm_to = $this->aHeadersValue[\MailSo\Mime\Enumerations\Header::TO_]; 
print_r($wm_to);
exit();