pantsarny

function fixJSON($json) {
    $regex = <<<'REGEX'
~
    "[^"\\]*(?:\\.|[^"\\]*)*"
    (*SKIP)(*F)
  | '([^'\\]*(?:\\.|[^'\\]*)*)'
~x
REGEX;

    return preg_replace_callback($regex, function($matches) {
        return '"' . preg_replace('~\\\\.(*SKIP)(*F)|"~', '\\"', $matches[1]) . '"';
    }, $json);
}