unpack(format,data)

Possible values:
可用值如下：

• a - NUL-padded string
  a - NUL- 字符串填满[padded string]
• A - SPACE-padded string
  A - SPACE- 字符串填满[padded string]
• h - Hex string, low nibble first
  h – 十六进制字符串，低“四位元”[low nibble first]
• H - Hex string, high nibble first
  H - 十六进制字符串，高“四位元”[high nibble first]
• c - signed char
  c – 带有符号的字符
• C - unsigned char
  C – 不带有符号的字符
• s - signed short (always 16 bit, machine byte order)
  s – 带有符号的短模式[short]（通常是16位，按机器字节顺序）
• S - unsigned short (always 16 bit, machine byte order)
  S – 不带有符号的短模式[short]（通常是16位，按机器字节排序）
• n - unsigned short (always 16 bit, big endian byte order)
  n -不带有符号的短模式[short]（通常是16位，按大endian字节排序）
• v - unsigned short (always 16 bit, little endian byte order)
  v -不带有符号的短模式[short]（通常是16位，按小endian字节排序）
• i - signed integer (machine dependent size and byte order)
  i – 带有符号的整数（由大小和字节顺序决定）
• I - unsigned integer (machine dependent size and byte order)
  I – 不带有符号的整数（由大小和字节顺序决定）
• l - signed long (always 32 bit, machine byte order)
  l– 带有符号的长模式[long]（通常是32位，按机器字节顺序）
• L - unsigned long (always 32 bit, machine byte order)
  L – 不带有符号的长模式[long]（通常是32位，按机器字节顺序）
• N - unsigned long (always 32 bit, big endian byte order)
  N – 不带有符号的长模式[long]（通常是32位，按大edian字节顺序）
• V - unsigned long (always 32 bit, little endian byte order)
  V– 不带有符号的长模式[long]（通常是32位，按小edian字节顺序）
• f - float (machine dependent size and representation)
  f –浮点（由大小和字节顺序决定）
• d - double (machine dependent size and representation)
  d – 双精度（由大小和字节顺序决定）
• x - NUL byte
  x – 空字节[NUL byte]
• X - Back up one byte
  X- 后面一个字节[Back up one byte]
• @ - NUL-fill to absolute position
  @ - NUL- 添加到一个绝对位置[absolute position]

<?php
$data = "PHP";
print_r(unpack("C*",$data));
?>

Array
(
[1] => 80
[2] => 72
[3] => 80
)

<?php
$data = "PHP";
print_r(unpack("C*myint",$data));
?>

Array
(
[myint1] => 80
[myint2] => 72
[myint3] => 80
)

<?php
$bin = pack("c2n2",0x1234,0x5678,65,66);
print_r(unpack("c2chars/n2int",$bin));
?>

Array
(
[chars1] => 52
[chars2] => 120
[int1] => 65
[int2] => 66
)