What does the b in front of string literals do?

Question

$binary = b\'Binary string\';

What consequences does it have to create a string as binary?

I couldn\'t find any hint about tha

Answer 1

Binary casting is available since 5.2.1 but will not take effect until 6.0 when unicode strings also take effect.

Which explains why this does nothing special right now for me on a server using 5.2.6: