You don't want to be developing code in PHP on a server that is not configured to display error messages.

谁都不想在一台没有配置成显示出错消息的服务器上用 PHP 开发代码。

youdao

It can also be used in some cases as a useful debugging tool: some Linux (or at least UNIX) utilities (and even daemons) do not display error messages, only the errno value.

在有些情况下，它还可作为有用的调试工具使用：有些Linux(至少是UNIX)实用程序(甚至是守护程序)不显示错误消息，而只显示errno值。

youdao

This is a way to display error messages or diagnostics; the code has a number of examples of diagnostic messages sent to this stream, many of them commented out in the release.

这是一种显示错误消息或诊断消息的方法；代码将大量诊断消息示例发送到这个流中，其中很多在发行版中已经被注释掉了。

youdao