How to Serialize a PHP Object to JSON

This function are simply awesome:
function getJsonData(){
    $var = get_object_vars($this);
    foreach($var as &$value){
        if(is_object($value) && method_exists($value,'getJsonData')){
            $value = $value->getJsonData();
        }
    }
    return $var;
}
source: StackOverflow