$re = '/(?<!\\\\)\\\\[{}]|(\{(?:"[^"\\\\]*(?:\\\\.[^"\\\\]*)*"|[^{}]*)(?:\\\\.(?:"[^"\\\\]*(?:\\\\.[^"\\\\]*)*"|[^{}]*))*})/';
$str = '{"asd"} - {"asd"}
\\{"test"}
- No match
\\\\{"Apple juice}"} - {"Apple juice}"}
{{"Test"}} - {"Test"}
{ddd"k"}';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php