PHP pack/unpack reference

Code	Description
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)
q	signed long long (always 64 bit, machine byte order)
Q	unsigned long long (always 64 bit, machine byte order)
J	unsigned long long (always 64 bit, big endian byte order)
P	unsigned long long (always 64 bit, little endian byte order)
f	float (machine dependent size and representation)
g	float (machine dependent size, little endian byte order)
G	float (machine dependent size, big endian byte order)
d	double (machine dependent size and representation)
e	double (machine dependent size, little endian byte order)
E	double (machine dependent size, big endian byte order)
x	NUL byte
X	Back up one byte
Z	NUL-terminated (ASCIIZ) string, will be NUL padded
@	NUL-fill to absolute position