Hello

I am trying to encode a mms from a php file, but there are some hex codes i don't understand.
Can anybody also check if i understood the other correctly

How can i calculate the header-length within PHP
How can i reproduce a content-length of 233 (=e9) to be 81 69

Here is a sample which i decoded from a mms i created. It contains just 1 text file. Basically to understand the basics before i continue.

8C 84 // message-type
98 30 30 31 00 // transaction-id: 001
8D 90 // version: 1.0
85 04 44 39 1F 54 // date
89 05 80 6D 6D 73 00 // from: mms
97 68 61 6D 69 64 00 // to: hamid
96 74 65 73 74 00 // subject: test
84 // Content-type
83 // text/plain
01 // number of entries
1A // ??
0B // content-length (11 bytes)
83 // ??
C0 // Content-id
22 // "
3C 68 61 6D 69 64 2E 74 78 74 3E 00 <hamid.txt>
8E // Content-location
68 61 6D 69 64 2E 74 78 74 00 // hamid.txt
74 65 73 74 20 69 74 20 6F 75 74 // test it out