A PHP docker image for CircleCI 2.0

$ php -v

PHP 7.1.9 (cli) (built: Sep  8 2017 02:43:40) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.1.0, Copyright (c) 1998-2017 Zend Technologies
    with Zend OPcache v7.1.9, Copyright (c) 1999-2017, by Zend Technologies
    with Xdebug v2.5.5, Copyright (c) 2002-2017, by Derick Rethans

$ php -m

[PHP Modules]
Core
ctype
curl
date
dom
fileinfo
filter
ftp
hash
iconv
json
libxml
mbstring
mysqlnd
openssl
pcre
PDO
pdo_mysql
pdo_sqlite
Phar
posix
readline
Reflection
session
SimpleXML
SPL
sqlite3
standard
tokenizer
xdebug
xml
xmlreader
xmlwriter
Zend OPcache
zip
zlib

[Zend Modules]
Xdebug
Zend OPcache

$ composer --version

Composer version 1.5.1 2017-08-09 16:07:22