sprintf %u gives wrong result

Question

Simple script, PHP 5.3.13, Windows 8, x32

<?php var_dump(sprintf('%u', -1380556906));

It gives me correct result

string(10) "2914410390"

the same thing with PHP 5.4.11, Freebsd 9.1, x64 gives

string(20) "18446744072328994710"

Why? How can I print signed int as unsigned int?

Answer 1

@Barmar has given the answer in the comments.

You are experiencing an unsigned integer overflow.

However as the integer size may vary in between architectures it is either 32 or 64 bits long.