src/Debug/FileStreamWrapper.php
public function stream_tell()
    {
        if (!$this->handle) {
            return false;
        }
        self::restorePrev();
        $position = \ftell($this->handle);
        self::register();
        return $position;
    }
public function stream_tell()
    {
        if (!$this->handle) {
            return false;
        }
        self::restorePrev();
        $position = \ftell($this->handle);
        self::register();
        return $position;
    }
Retrieve the current position of a stream

@return integer

@see http://php.net/manual/en/streamwrapper.stream-tell.php