public function setPrivateKey($path)
    {
        if(!file_exists($path)) {
            throw new \InvalidArgumentException('the private key file does\'t exist');
        }

        $this->privateKey = file_get_contents($path);

        return $this;
    }
public function setPrivateKey($path)
    {
        if(!file_exists($path)) {
            throw new \InvalidArgumentException('the private key file does\'t exist');
        }

        $this->privateKey = file_get_contents($path);

        return $this;
    }
public function setPrivateKey ( $ path ) { if ( ! file_exists ( $ path ) ) { throw new \ InvalidArgumentException ( 'the private key file does\'t exist' ) ; } $ this -> privateKey = file_get_contents ( $ path ) ; return $ this ; }
set private key
@param string $path  the private key file path
@throws \InvalidArgumentException when the private key file does'n exist
set private key