When testing an answer for another user's question I found something I don't understand. The problem was to replace all literal
r characters from a string with a single space.
Now, the first pattern I tried was:
which surprisingly didn't work. I tried the same pattern in Perl and it worked fine. After some trial and error I found that PHP wants 3 or 4 backslashes for that pattern to match, as in:
these patterns - to my surprise - both work. Why are these extra backslashes necessary?