I'm certain this is a duplicate, but can't find it. And because comments go ignored, I'll just add it as answer again.
If you need to decode a Javascript expression (it doesn't have key quotes as JSON would require it) you can use:
http://pear.php.net/package/Services_JSON
which has some fallback logic to process unquoted keys
http://include-once.org/p/upgradephp/#upgrade.php.prefixed
with up_json_decode($json, FALSE, 512, JSON_PARSE_JAVASCRIPT)
As inadvisable alternative there are some regex and string patching workarounds for pre-processing unquoted keys.