hash_djb2 PHP结果错误

C++

unsigned int hash_djb2(char *str, unsigned int str_size)
{
    unsigned int hash = 5381;
    for(unsigned int c = 0; c < str_size; c++)
        hash = ((hash << 5) + hash) + str[c];
    return (hash & 0xFFFFFFFF);
}
int main()
{
    string term = "one piece";
    char* data = const_cast<char*>(term.c_str());
    printf("%u", hash_djb2(data, term.size()));//2850035213
}

PHP

<?php
    function hash_djb2($str)
    {
        $hash = 5381;
        $length = strlen($str);
        for($i = 0; $i < $length; $i++) {
            $hash = ( ($hash << 5) + $hash ) + $str[$i];
        }
        return ($hash & 0xFFFFFFFF);
    }
    echo hash_djb2("one piece");//-233010523
?>

如何使PHP返回与C++相同的结果？