将字符串转换为JSON

Is there any way to make PHP look at a string as a JSON?
I have a string, in a JSON format of course, and I want to perform actions on it like it was an array. However I don't want to use CJSON::decode because it takes a long time, Is there a way?
Example for the string:

{"myArray":[{"key1":"val1","key2":"val2","key3":"val3","key4":"val4"},
{"key1":"val2_1","key2":"val2_2","key3":"val2_3","key4":"val2_4"}]}

how about json_decode() ?

I don't think there is faster than that

$string = '{"myArray":[{"key1":"val1","key2":"val2","key3":"val3","key4":"val4"},    {"key1":"val2_1","key2":"val2_2","key3":"val2_3","key4":"val2_4"}]}';
$array = json_decode($string);

Not sure what CJSON::decode is but you have to decode the string so you can use the built in function json_decode($str);