Test if string is URL encoded in PHP

Question

How can I test if a string is URL encoded?

Which of the following approaches is better?

• Search the string for characters which would be encoded, which

Answer 1

Here is something i just put together.

if ( urlencode(urldecode($data)) === $data){
    echo 'string urlencoded';
} else {
    echo 'string is NOT urlencoded';
}