The plugin generated 2 characters of unexpected output during activation.
自己開發的插件，啟動時出現以下錯誤： The plugin generated 2 characters of […]
自己开发的插件，激活时出现以下错误：
The plugin generated 2 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.
后来发现，在两个php文件的开头各有一个空格，删掉之后，就没事了。
