AWS S3 QueryString Authorization - php

Question

Background
I am trying to create a signed url to fetch a resource from AWS S3. There are several examples in aws s3 documentation , and as a first step I am trying to replicate the last example on that page.
My code is :
$access_key = "AKIAIOSFODNN7EXAMPLE";
$secret_key = "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY";
$string_to_sign = "GET\n\n\n1175139620\n/johnsmith/photos/puppy.jpg";
$encode = hash_hmac('sha1', utf8_encode($string_to_sign) , $secret_key) ;
echo base64_encode($encode). "\r\n" ;
The above code outputs
MzY5ODAyOGU3MGYzYWNjZjk2MTczYTA0MzU3OWE5MzQzNTJjNGE3Zg==
According to the example, the result should be
NpgCjnDzrM%2BWFzoENXmpNDUsSn8%3D&
I do understand that the result needs to be url encoded , but I think I am still far off. Can I get some help please ?

Answer 1

I found the solution
$encode = hash_hmac('sha1', utf8_encode($string_to_sign), $secret_key);
is replaced by
$encode = hash_hmac('sha1', utf8_encode($string_to_sign), $secret_key, true );
Final script to simulate the example is :
$access_key = "AKIAIOSFODNN7EXAMPLE";
$secret_key = "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY";
$string_to_sign = "GET\n\n\n1175139620\n/johnsmith/photos/puppy.jpg";
$encode = hash_hmac('sha1', utf8_encode($string_to_sign), $secret_key , true ) ;
echo urlencode(base64_encode($encode)) . "\r\n" ;