openssl_sign()的结果是如何编码的?

它似乎根本没有编码:

openssl_sign($data, $signature, $private_key, OPENSSL_ALGO_SHA1);
echo $signature;

生产:

p}+C&3�\˅��u�gh��X������j��Yx���e�?�l�j��\�a/d�3}��t�l�w�

或:

00000000  05 70 7d 2b 43 26 33 d1  5c cb 85 ff b0 75 c6 67  |.p}+C&3.\....u.g|
00000010  68 d2 d6 58 87 8f 02 f2  bc e5 f9 6a ff c4 59 78  |h..X.......j..Yx|
00000020  bc 85 b4 13 65 fe 3f 00  d0 15 6c e7 6a b1 93 5c  |....e.?...l.j..\|
00000030  88 61 2f 64 f8 33 7d b1  ad 74 01 e1 6c d9 77 c4  |.a/d.3}..t..l.w.|
00000040