Big/little endian assumptions.

[bbkr]

Following code https://github.com/krowinski/php-mysql-replication/blob/master/src/MySQLReplication/BinaryDataReader/BinaryDataReader.php#L72 works by accident because s uses native architecture. And every Intel/AMD CPU is in little endian architecture which is the same as binlog bytes layout.

Architecture should be forced in unpack pattern ( s< - like in Perl, I'm not sure if PHP supports it).
Or native architecture should be checked and bytes reversed before unpacking in case of mismatch.