How to write a recursive regex that matches nested parentheses?

Question

I am trying to write a regexp which matches nested parentheses, e.g.:

\"(((text(text))))(text()()text)(casual(characters(#$%^^&&#^%#@!&**&#^*         


        

Answer 1

When I found this answer I wasn't able to figure out how to modify the pattern to work with my own delimiters which where { and }. So my approach was to make it more generic.

Here is a script to generate the regex pattern with your own variable left and right delimiters.

$delimiter_wrap  = '~';
$delimiter_left  = '{';/* put YOUR left delimiter here.  */
$delimiter_right = '}';/* put YOUR right delimiter here. */

$delimiter_left  = preg_quote( $delimiter_left,  $delimiter_wrap );
$delimiter_right = preg_quote( $delimiter_right, $delimiter_wrap );
$pattern         = $delimiter_wrap . $delimiter_left
                 . '((?:[^' . $delimiter_left . $delimiter_right . ']++|(?R))*)'
                 . $delimiter_right . $delimiter_wrap;

/* Now you can use the generated pattern. */
preg_match_all( $pattern, $subject, $matches );