I told you it was a cheap hack, NogDog I really don't even know how 'euro' appears on his pages, so I'm not sure how to match it. It probably should at least match the plural as well, which would be '/euro(s?)/g', and your case-sensitivity point is well-taken, so make it '/euro(s?)/gi' I'll leave it to the OP to download Edmund Weitz' The Regex Coach or visit regex101.com.
I think maybe I told a story about a designer who put a page up with inline CSS and every block-level element (and some SPANs as well, which were also highly over-used) had "font-family:times" in it, on a site where the CSS sheets were all sans-serif fonts. We went round & round about its appropriateness in the office in full hearing of the VP IT and pretty much everyone else too.
Beyond that, let's just say that I'm pretty good with cheap hacks like this one, and I know how to have PHP only serve it to people outside our offices ... #what_she_dont_know_wont_hurt, right?