How does php read input by byte?

How does php read input data in bytes? the first 4 bytes are numbers, 4 bytes are strings, and then 4 bytes are strings; why ?, If you are talking about the fixed length of each segment (4 bytes) $ ar = str_split ($ _ POST ['variable name'], 4 ); how to read the input in bytes for each php segment

Because someone else post the data.
The first four bytes are numbers.

4 bytes later than string

The last four bytes are different.
Why?

------ Solution --------------------
If you are talking about the fixed length of each segment (4 bytes)
$ Ar = str_split ($ _ POST ['variable name'], 4 );

If the length of each segment is not long
For example, 1, 2, 3, 4, 5
Then
$ Mask = array (1, 2, 3, 4, 5 );
$ S = $ _ POST ['variable name'];
$ N = 0;
For ($ I = 0; $ I $ Ar [] = substr ($ s, $ n, $ mask [$ I]);
$ N + = $ mask [$ I];
}



------ Solution --------------------
$ _ POST ['id'] [0]
$ _ POST ['id'] [1]
$ _ POST ['id'] [2]
$ _ POST ['id'] [3]

You can traverse it cyclically.