正则表达式帮助 - 括号内的括号

Question

I'm trying to develop a function that can sort through a string that looks like this:

Donny went to the {park|store|{beach with friends|beach alone}} so he could get a breath of fresh air. 

What I intend to do is search the text recursively for {} patterns where there is no { or } inside the {}, so only the innermost sandwiched text is selected, where I will then run a php to array the contents and select one at random, repeating process until the whole string has been parsed, showing a complete sentence.

I just cannot wrap my head around regular expressions though.

Appreciate any help!

Answer 1

Regular expressions don't deal well with recursive stuff, but PHP does:

$str = 'Donny went to the {park|store|{beach with friends|beach alone}} so he could get a breath of fresh air.';

echo parse_string($str), "
";

function parse_string($string) {
    if ( preg_match('/\{([^{}]+)\}/', $string, $matches) ) {
        $inner_elements = explode('|', $matches[1]);
        $random_element = $inner_elements[array_rand($inner_elements)];
        $string = str_replace($matches[0], $random_element, $string);
        $string = parse_string($string);
    }
    return $string;
}