Relationship of R/S points in between signed message and DER signature

this time is difficult for me to explain problem i was facing. i realize that R/S point in DER signature is not match to the 1 in bitcoin signed message? Ok below is my say signed message.

Об этом сообщает Московский репортер

——BEGIN BITCOIN SIGNED MESSAGE—— c4ca4238a0b923820dcc509a6f75849b ——BEGIN SIGNATURE—— 1BxqqjVC29fvCWin4qBuqZhBy4V7Ncdxby IPnTEOU713+XclrBrUEfTLeP0A7QIR4lObzQjBjyxGQExPwkalrQK1JOggIWk4xrfWIjHEC0RKGv3vtguDfto0o= ——END BITCOIN SIGNED MESSAGE——

my working way is $decoded_content = bin2hex(base64_decode(IPnTEOU713+XclrBrUEfTLeP0A7QIR4lObzQjBjyxGQExPwkalrQK1JOggIWk4xrfWIjHEC0RKGv3vtguDfto0o=))

then i manage to get R/S point from $decoded_content. after that, i use R/S point to generate DER signature. I realized that this DER signature is fail in signature verification.

shortly to say,

my program check valid signature using function in https://github.com/tuaris/CryptoCurrencyPHP/blob/master/Wallet.class.php#L225

therefore. if i have another party send me DER signature, how do i convert it to get base64_encoded string, so end up i am able to use function i mention just now.

I try alot of methods but no luck, are R/S points in both signed message and DER signature means to same?

please help