php - How to improve the regex?

Question

I'm trying to match the following possibilities with a regex:

MORE THAN CAD 10,000
MORE THAN CAD 10,000 BUT LESS THAN CAD 15,000
LESS THAN CAD 10,000

My regex works with /^(((MORE|LESS) THAN CAD [d,]+)|(MORE THAN CAD [d,]+ BUT LESS THAN CAD [d,]+))$/ but I'm wondering if there's a more elegant way.

I've tried /^(MORE THAN CAD [d,]+)?(( BUT )?LESS THAN CAD [d,]+)?$/ but it's letting the following pass as well:

MORE THAN CAD 10,000LESS THAN CAD 15,000

question from:https://stackoverflow.com/questions/65832261/how-to-improve-the-regex

Answer 1

You can use

^(?:(MORE)|LESS) THAN CAD [d,]+(?(1)(?: BUT LESS THAN CAD [d,]+)?)$

See the regex demo.

Details:

• ^ - start of string
• (?:(MORE)|LESS) - a non-capturing group matching MORE (captured in Group 1) or LESS
• THAN CAD - a literal string
• [d,]+ - one or more digits or commas
• (?(1)(?: BUT LESS THAN CAD [d,]+)?) - a conditional that allows matching an optional BUT LESS THAN CAD [d,]+ pattern if Group 1 matched.
• $ - end of string.