在非标准位置使用composer和php

我正在尝试在我的NAS上使用composer（一个很好的旧D-Link DNS-23，运行非常好的fonz fun plug 0.7）。

我在/ffp/bin/php中安装了php。

当我使用以下命令安装composer时

 php -r "readfile('https://getcomposer.org/installer');" | php -- --install-dir=/ffp/sbin --filename=composer

但当我做一个简单的less /ffp/sbin/composer时，我有以下shebang集：

#!/usr/bin/env php
<?php
/*
 * This file is part of Composer.
 *

不幸的是，我的NAS上没有/usr/bin/env文件夹。。。那么，如何让composer引用正确的php可执行文件呢？

此外，我尝试将声明更改为使用#!/ffp/bin/php，但在这样做时，任何composer运行都会返回以下结果：

PHP Warning:  PHP Startup: Unable to load dynamic library '/ffp/lib/php/extensions/no-debug-non-zts-20100525/gd.so' - File not found in Unknown on line 0
Warning: PHP Startup: Unable to load dynamic library '/ffp/lib/php/extensions/no-debug-non-zts-20100525/gd.so' - File not found in Unknown on line 0
PHP Warning:  PHP Startup: Unable to load dynamic library '/ffp/lib/php/extensions/no-debug-non-zts-20100525/sqlite.so' - File not found in Unknown on line 0
Warning: PHP Startup: Unable to load dynamic library '/ffp/lib/php/extensions/no-debug-non-zts-20100525/sqlite.so' - File not found in Unknown on line 0
PHP Fatal error:  Uncaught exception 'PharException' with message 'phar "/mnt/HD_a2/ffp/sbin/composer" has a broken signature' in /mnt/HD_a2/ffp/sbin/composer:23
Stack trace:
#0 /mnt/HD_a2/ffp/sbin/composer(23): Phar::mapPhar('composer.phar')
#1 {main}
  thrown in /mnt/HD_a2/ffp/sbin/composer on line 23
Fatal error: Uncaught exception 'PharException' with message 'phar "/mnt/HD_a2/ffp/sbin/composer" has a broken signature' in /mnt/HD_a2/ffp/sbin/composer:23
Stack trace:
#0 /mnt/HD_a2/ffp/sbin/composer(23): Phar::mapPhar('composer.phar')
#1 {main}
  thrown in /mnt/HD_a2/ffp/sbin/composer on line 23

特别重要的是线路

PHP Fatal error:  Uncaught exception 'PharException' with message 'phar "/mnt/HD_a2/ffp/sbin/composer" has a broken signature' in /mnt/HD_a2/ffp/sbin/composer:23

我该怎么修？换句话说，如何在NAS上安装一个可工作的php+composer？