pack | Functions | PHP

Pack data into binary string

Syntax

pack ( string $format [, mixed $... ] ) : string

Parameters

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.

Code	Description
a	NUL-padded string
A	SPACE-padded string
c	signed char
C	unsigned char
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)
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)
h	Hex string, low nibble first
H	Hex string, high nibble first
i	signed integer (machine dependent size and byte order)
I	unsigned integer (machine dependent size and byte order)
J	unsigned long long (always 64 bit, big endian byte order)
l	signed long (always 32 bit, machine byte order)
L	unsigned long (always 32 bit, machine byte order)
n	unsigned short (always 16 bit, big endian byte order)
N	unsigned long (always 32 bit, big endian byte order)
P	unsigned long long (always 64 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)
s	signed short (always 16 bit, machine byte order)
S	unsigned short (always 16 bit, machine byte order)
v	unsigned short (always 16 bit, little endian byte order)
V	unsigned long (always 32 bit, little endian byte order)
x	NUL byte
X	Back up one byte
Z	NUL-padded string
@	NUL-fill to absolute position

...

Return

Returns a binary string containing data.

Examples

1

<?

$format = "nvc*";
$return = pack($format, 0x1234, 0x5678, 65, 66);

print_r(unpack("c6", $return));

?>

Array
(
    [1] => 18
    [2] => 52
    [3] => 120
    [4] => 86
    [5] => 65
    [6] => 66
)

2

<?

$format = "nvc*";
$return = pack($format, 0x1234, 0x5678, 65, 66);

print_r(unpack("H12", $return));

?>

Array
(
    [1] => 123478564142
)

Links

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