Composer is not working的问题出现的原因是在安装Composer时将其安装为全局的独立应用程序。解决方法是运行composer require intervention/image命令，而不是使用php composer require intervention/image命令。原作者之前习惯在composer命令前面添加php并且一直正常工作，不确定发生了什么变化。

Composer is a popular dependency management tool for PHP. However, sometimes users may encounter issues where Composer is not working properly. In this article, we will discuss the possible reasons for this problem and provide a solution.

One possible reason for Composer not working could be that it is not installed correctly. To resolve this issue, you can try the following steps:

1. Open your terminal window.

2. Execute the following command:

$ curl -sS https://getcomposer.org/installer | php

This command will download the Composer installer script and execute it using PHP.

3. Next, execute the following command to move the downloaded file to the appropriate location:

$ sudo mv composer.phar /usr/local/bin/composer

This command will move the Composer executable to the /usr/local/bin directory, which is commonly included in the system's PATH.

Once you have completed these steps, you should be able to use Composer by typing `composer` in the terminal, instead of `php composer ...`.

For more information and source of this solution, you can refer to this source.

By following these steps, you should be able to resolve the issue of Composer not working.