PHP regex delimiter, what's the point?

Question

Why do PHP regexes have the surrounding delimiters? It seems like it would be more clear if any pattern modifiers were passed in as a parameter to whatever function was being used.

Answer 1

The reason for the delimiter is to put flags after the pattern. Arguably flags could be passed as a separate parameter (Java can do it this way) but that's the way Perl did it originally (and sed/awk/vi before it) so that's how it's done now.

Don't use forward slashes: they're too common. Personally I nearly always use the ! character. I'm hardly ever looking for that.

Answer 2

There is no technical reason why it has to be like this.

As noted in a comment, the underlying library does not require that flags be passed as part of the regexp - in fact, the extension has to strip these off and pass them as a separate argument.

It appears as though the original implementer was trying to make it look like grep/sed/awk/perl/etc so that it is more familiar to programmers coming from those tools.