Question

I have a regular expression that is used to re-define a constant in php file using preg_match and input file is screened using htmlspecialchars
eg for

define('MEMBERSHIP', 'GOLD'); 

the following regex works

/define.*[&quote\']' . $constant . '[&quote;\'].*;/i

however it matches the last semi colon, works in most scenarios but fails in a case like the following
eg:

define("MEMBERSHIP", 'GOLD'); // membership subscription; empty means not in use.

notice the last semicolon, resulting in replaced code as

define("MEMBERSHIP", 'SILVER'); empty means not in use.

which breaks the code. tried the regex below but it didn’t work for those with double quote

/define.*[&quote;\']' . $constant . '[&quote;\'][^;]*;/i

any idea how to fix this?

Answer 1

You can match corresponding quotes by using a backreference:

'/define[^"\']*(["\'])' . $constant . '\1[^;]*;/i'

Otherwise, the negated character class you have at the end is definitely the way to go.