<?php
$input = <<<INP
value that I {want}, vs value "I do {NOT} want".
Let's make it {nested {this {time}}}
And yes, it's even "{bullet-{proof}}" :)
INP;
@preg_match_all('~(\').*?\1(*SKIP)(*FAIL)|\{(?:[^{}]|(?R))*\}~', $input, $m);
print_r($m[1]);
?>