installer does not check all extensions

[glensc]

$ curl -LSs https://box-project.github.io/box2/installer.php | php
Box Installer
=============

Environment Check
-----------------

"-" indicates success.
"*" indicates error.

 - You have a supported version of PHP (>= 5.3.3).
 - You have the "phar" extension installed.
 - You have a supported version of the "phar" extension.
 - You have the "openssl" extension installed.
 * Notice: The "phar.readonly" setting needs to be off to create Phars.
 - The "detect_unicode" setting is off.
 - The "allow_url_fopen" setting is on.

Everything seems good!

Download
--------

 - Downloading manifest...
 - Reading manifest...
PHP Fatal error:  Call to undefined function json_decode() in - on line 151
ERROR: Build failed: exit code 1

[glensc]

also seems iconv is required, mbstring is optional

$ php -d phar.readonly=0 box.phar build src

PHP Fatal error:  Call to undefined function Symfony\Polyfill\Mbstring\iconv() in phar:///builds/ed/php-parallel-lint/box.phar/src/vendors/symfony/polyfill-mbstring/Mbstring.php on line 513

[glensc]

and filter ext is required

$ php -d phar.readonly=0 box.phar build -c src/box.json
PHP Fatal error:  Call to undefined function Phine\Path\filter_var() in phar:///builds/ed/php-parallel-lint/box.phar/src/vendors/phine/path/src/lib/Phine/Path/Path.php on line 146
ERROR: Build failed: exit code 1

[glensc]

and tokernizer!

$ php -d phar.readonly=0 box.phar build -c src/box.json
Building...
PHP Fatal error:  Call to undefined function Herrera\Box\Compactor\token_get_all() in phar:///builds/ed/php-parallel-lint/box.phar/src/vendors/herrera-io/box/src/lib/Herrera/Box/Compactor/Php.php on line 46
ERROR: Build failed: exit code 1