Is there a way to back reference in the regular expression pattern?
Example input string:
Here is "some quoted" text.
Say I want to pull out the quoted text, I could create the following expression:
"([^"]+)"
This regular expression would match some quoted.
Say I want it to also support single quotes, I could change the expression to:
["']([^"']+)["']
But what if the input string has a mixture of quotes say Here is 'some quoted" text. I would not want the regex to match. Currently the regex in the second example would still match.
What I would like to be able to do is if the first quote is a double quote then the closing quote must be a double. And if the start quote is single quote then the closing quote must be single.
Can I use a back reference to achieve this?
My other related question: Getting text between quotes using regular expression
You can make use of the regex:
(["'])[^"']+\1
() : used for grouping[..] : is the char class. so ["']
matches either " or ' equivalent
to "|'[^..] : char class with negation.
It matches any char not listed after
the ^+ : quantifier for one or more\1 : backreferencing the first
group which is (["'])In PHP you'd use this as:
preg_match('#(["\'])[^"\']+\1#',$str)