pack
(PHP 4, PHP 5)
pack — Pack data into binary string
说明
string pack
( string $format
[, mixed $args
[, mixed $…
]] )
Pack given arguments into a binary string according to
format.
The idea for this function was taken from Perl and all formatting codes
work the same as in Perl. However, there are some formatting codes that are
missing such as Perls “u” format code.
Note that the distinction between signed and unsigned values only
affects the function unpack(), where as
function pack() gives the same result for
signed and unsigned format codes.
参数
format
The format string consists of format codes
followed by an optional repeater argument. The repeater argument can
be either an integer value or * for repeating to
the end of the input data. For a, A, h, H the repeat count specifies
how many characters of one data argument are taken, for @ it is the
absolute position where to put the next data, for everything else the
repeat count specifies how many data arguments are consumed and packed
into the resulting binary string.
Currently implemented formats are:
pack() format characters
Code
Description
a
NUL-padded string
A
SPACE-padded string
h
Hex string, low nibble first
H
Hex string, high nibble first
csigned 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
Z
NUL-padded string (new in PHP 5.5)
@
NUL-fill to absolute position
args
返回值
Returns a binary string containing data.
更新日志
版本
说明
5.5.0
The “Z” code was added with equivalent functionality to “a” for Perl
compatibility.
范例
Example #1 pack() example
$binarydata
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