php - 包 ('i' ,1) 总是 4 个字节吗？

Question

在我的机器上 PHP_INT_SIZE 是 8 但 pack('i',1) 无论如何都会返回一个 4 字节的字符串。

The docs说 i 是一个“有符号整数(取决于机器的大小和字节顺序)”，但这似乎不是真的。是否固定为4字节？

这意味着在 64 位机器上 unpack('i',pack('i',PHP_INT_MAX))[1] !== PHP_INT_MAX 因为一半的数据被砍掉了。

Answer 1

重要的是要记住 PHP is written in C (换句话说，PHP 认为 int 是什么并不重要)。跳出关于 sizeof(int) 的另一个答案，它看起来像是 32 位的遗物 C compilers (强调我的)

Yes, it depends on both processors (more specifically, ISA, instruction set architecture, e.g., x86 and x86-64) and compilers including programming model. For example, in 16-bit machines, sizeof (int) was 2 bytes. 32-bit machines have 4 bytes for int. It has been considered int was the native size of a processor, i.e., the size of register. However, 32-bit computers were so popular, and huge number of software has been written for 32-bit programming model. So, it would be very confusing if 64-bit computer would have 8 bytes for int. Both Linux and Windows remain 4 bytes for int. But, they differ in the size of long.

所以，简而言之，它可以是 2 个字节，但前提是你有一个 16 位处理器。在 32 位和 64 位系统中，C 似乎在所有情况下都说 int 是 4 个字节。所以，是的，pack('i',1); 将始终为 4 个字节。