selenium2 for composer install facing with phalcon/incubator error in PHP -

i using window command prompt,when update composer facing below error

c:\xampp\htdocs\myproject>composer update warning: development build of composer on 60 days old. recommend ed update running "c:\programdata\composersetup\bin\composer.phar self- update" latest version. loading composer repositories package information updating dependencies (including require-dev) failed decode response: zlib_decode(): data error retrying degraded mode, check https://getcomposer.org/doc/articles/troubles hooting.md#degraded-mode more info requirements not resolved installable set of packages.   problem 1     - installation request phalcon/incubator dev-master -> satisfiable ph alcon/incubator[dev-master].     - phalcon/incubator dev-master requires ext-phalcon >=2.0.4 -> requested  php extension phalcon missing system. 

the last line should give clue: haven't yet installed phalconphp on system, required incubator package.

also, run composer self-update recommended.