Problem with ZFTool: module (ZFTool) cannot be initialized

ZFTool is a maintenance tool for Zend Framework applications. There are several ways to install it. I am using it from a PHAR file.

$ mkdir -p /usr/lib/ZendFramework/zftool
$ cd /usr/lib/ZendFramework/zftool
$ wget http://packages.zendframework.com/zftool.phar
$ ln -s  /usr/lib/ZendFramework/zftool/zftool.phar /usr/bin/zf
$ chmod 755 /usr/bin/zf

It works when I run the tool outside of the ZF application. But now I tried this in the application and got this error:

root@devvm:/usr/lib/ZendFramework/test# cd /path/to/application/ root@devvm:/path/to/application# zf PHP Fatal error:  Uncaught exception 'Zend\ModuleManager\Exception\RuntimeException' with message 'Module (ZFTool) could not be initialized.' in /path/to/application/vendor/zendframework/zendframework/library/Zend/ModuleManager/ModuleManager.php:175 Stack trace:
#0 /path/to/application/vendor/zendframework/zendframework/library/Zend/ModuleManager/ModuleManager.php(149): Zend\ModuleManager\ModuleManager->loadModuleByName(Object(Zend\ModuleManager\ModuleEvent))
#1 /path/to/application/vendor/zendframework/zendframework/library/Zend/ModuleManager/ModuleManager.php(90): Zend\ModuleManager\ModuleManager->loadModule('ZFTool')
#2 [internal function]: Zend\ModuleManager\ModuleManager->onLoadModules(Object(Zend\ModuleManager\ModuleEvent))
#3 /path/to/application/vendor/zendframework/zendframework/library/Zend/EventManager/EventManager.php(468): call_user_func(Array, Object(Zend\ModuleManager\ModuleEvent))
#4 /path/to/application/vendor/zendframework/zendframework/library/Zend/EventManager/EventManager.php( in /path/to/application/vendor/zendframework/zendframework/library/Zend/ModuleManager/ModuleManager.php on line 175

Why is this happening? How to avoid this behavior?