php ftp警告权限

I'm writing a class that will show a list of files and retrieve / send files. I have problem with downloading. I can connect with server, showing list files, but I can't download file.

Warning: ftp_get(index.php): failed to open stream: Permission denied in /var/www/public_html/class.ftp.php on line 51
Warning: ftp_get(): Error opening index.php in /var/www/public_html/class.ftp.php on line 51

When I use application in my PC and this account ftp, I don't have problem with downloading. In principle, I cannot change file permissions, because I will be used multiple ftp. I don't understand, why I don't need change a permission file when I download file with application and PHP needs this permission have.

Code:

protected function connect()
{
    $this->connect=ftp_connect($this->host);
    $result=ftp_login($this->connect, $this->login, $this->pass);
    if($result){
        ftp_pasv($this->connect, true);
        $this->status=true;
    }
    else $this->status=false;
}
public function download_file($path)
{
    $e=explode('/', $path);

    $last=count($e)-1;
    $file=$e[$last];
    $file='download/'.$file;

    return ftp_get($this->connect, $path, $file, FTP_ASCII); //I tried FTP_BINARY
}

Use:

var_dump($conn->download_file('index.php'));

See:

bool(false)

And of course errors.

Ok my sweet mistake ;-)

1) change local file to server file...

public function download_file($path)
{

    $file='./download/'.$path;
    return ftp_get($this->connect, $file, $path, FTP_BINARY);
}

2) My local folder "downloads" must have chmod 777

Sorry