In a response to this post on the PHP 10.0 Blog, Richard Heyes offers a method for what Stas was wanting:

OK, then what we do if something weird happens in production and we want to see the errors, but we don't want others to see them? [...] Maybe PHP could have some setting like display_errors=local which would enable display_errors for requests originating from developer machine but would disable it when outsider accesses it?

Richard's solution checks the HTTP_HOST value of the current request and, based on whether it's marked as "live" or "dev", uses a ini_set to change the display_errors setting to true/false.

In an effort to get some thought going about ways to encourage security in PHP applications, Stas has posted an idea about a simplified php.ini setting - production=On.

His idea is that, with this setting on, the PHP installation would:

• disable display errors
• disable phpinfo()
• turn expose_php off
• make max_execution_time/memory_limit reasonable
• and possibly a few others that some developers forget to set correctly