Regular Expression to match unlimited number of options

Question

I want to be able to parse file paths like this one:

 /var/www/index.(htm|html|php|shtml)

into an ordered array:

 array("htm", "html", "php", "shtml")

and then produce a list of alternatives:

/var/www/index.htm
/var/www/index.html
/var/www/index.php
/var/www/index.shtml

Right now, I have a preg_match statement that can split two alternatives:

 preg_match_all ("/\(([^)]*)\|([^)]*)\)/", $path_resource, $matches);

Could somebody give me a pointer how to extend this to accept an unlimited number of alternatives (at least two)? Just regarding the regular expression, the rest I can deal with.

The rule is:

• The list needs to start with a ( and close with a )

• There must be one | in the list (i.e. at least two alternatives)

• Any other occurrence(s) of ( or ) are to remain untouched.

Update: I need to be able to also deal with multiple bracket pairs such as:

 /var/(www|www2)/index.(htm|html|php|shtml)

sorry I didn't say that straight away.

Update 2: If you're looking to do what I'm trying to do in the filesystem, then note that glob() already brings this functionality out of the box. There is no need to implement a custom solutiom. See @Gordon's answer below for details.

Answer 1

I think you're looking for:

/(([^|]+)(|([^|]+))+)/

Basically, put the splitter '|' into a repeating pattern.

Also, your words should be made up 'not pipes' instead of 'not parens', per your third requirement.

Also, prefer + to * for this problem. + means 'at least one'. * means 'zero or more'.

Answer 2

Not exactly what you are asking, but what's wrong with just taking what you have to get the list (ignoring the |s), putting it into a variable and then explodeing on the |s? That would give you an array of however many items there were (including 1 if there wasn't a | present).