src/Debug/Utilities.php
public static function getResponseHeader($key = 'Content-Type')
    {
        $value = null;
        $headers = \headers_list();
        foreach ($headers as $header) {
            if (\preg_match('/^'.$key.':\s*([^;]*)/i', $header, $matches)) {
                $value = $matches[1];
                break;
            }
        }
        return $value;
    }
public static function getResponseHeader($key = 'Content-Type')
    {
        $value = null;
        $headers = \headers_list();
        foreach ($headers as $header) {
            if (\preg_match('/^'.$key.':\s*([^;]*)/i', $header, $matches)) {
                $value = $matches[1];
                break;
            }
        }
        return $value;
    }
Returns a sent/pending response header value

@param string $key default = 'Content-Type', header to return

@return string
@req    php >= 5