pack() 函数把数据装入一个二进制字符串。
pack(format,args+)
| 参数 | 描述 |
|---|---|
| format | 必需。规定在包装数据时所使用的格式。 |
| args+ | 可选。规定被包装的一个或多个参数。 |
format 参数的可能值：
a - NUL-padded string
A - SPACE-padded string
h - Hex string, low nibble first
H - Hex string, high nibble first
c - signed char
C - unsigned char
s - signed short (always 16 bit, machine byte order)
S - unsigned short (always 16 bit, machine byte order)
n - unsigned short (always 16 bit, big endian byte order)
v - unsigned short (always 16 bit, little endian byte order)
i - signed integer (machine dependent size and byte order)
I - unsigned integer (machine dependent size and byte order)
l - signed long (always 32 bit, machine byte order)
L - unsigned long (always 32 bit, machine byte order)
N - unsigned long (always 32 bit, big endian byte order)
V - unsigned long (always 32 bit, little endian byte order)
f - float (machine dependent size and representation)
d - double (machine dependent size and representation)
x - NUL byte
X - Back up one byte
@ - NUL-fill to absolute position
例子例子 1
输出：
PHP
例子 2
输出：
PHP
