bcompiler encodes your source into bytecode. It does not encrypt your code.
It does increase the performance of your code, as PHP processes raw source into bytecode before execution anyway.
No one will be able to decode the bytecode back to your code.
See the answers to this question which provide links to other tools which may be an extension to bcompiler.
Also, as this answer suggests:
It is just as safe as compiling C++ to ASM. It CAN be reverse
engineered or understood by careful reading and logic, ...
I tried the "bcompiler decoder", linked to in this answer. When bcompiling a class, then decompiling it with the "bcompiler decoder", a set of human readable instructions are created. It did not reproduce a class with the same behavior as the source/bcompile'd version (which would've been pretty impressive).