Well, PHP is certainly efficient for programming websites. It just comes at the expense of everything else.
Yes, bashing PHP is fun, and yes, I do it all the time. PHP may be a joke, but there are a bunch of PHP websites because PHP is a very, very fast way to program websites, even widely used ones.
If you could program a simple website in Idris in 30 minutes starting from no prior knowledge, then a large amount of websites would be programmed in Idris (and the world would be a much nicer place). Since that's not the case, should we consider Idris a bad language with major downsides? Of course not, that's pointless, since it wasn't a language meant for building websites. PHP, however, is. Saying it has major downsides outside of its niche is somewhat irrelevant.