echo - Strange print behaviour in PHP?

Refer to href="http://php.net/manual/en/language.operators.bitwise.php#example-115"
rel="nofollow">Bitwise
Operators:

We have to find
4 << 5. It means shift the bits of 4 5 times to the
left:

4 is
            00000000000000000000000000000100
4 << 5 after shifting is
            00000000000000000000000010000000
00000000000000000000000010000000 is 2^7 =
            2*2*2*2*2*2*2 = 128