Add a bit more error checking around loading the Trustly publickey
Look for the error messages in the correct location
Add displaycurrency to p2p API call
There is no variable named that
Silence the load error and properly handle the return falue beeing FALSE, not NULL
Whitespace
Add the Hello call for the Signed and Unsigned API.

Use this to test connectivity to the API.

This is really an altogether unsigned call, so we will call it by
creating an unsigned API from the Signed API during the call.
Default data to NULL when constructing, we will not always have it
PHP < 5.3 compability fixes.
$signature_alg argument for openssl_verify() was added in 5.2.0, check for this. Check for the existance of the never curl options before using them.