PHP pack() Function

❮ PHP Misc Reference

Example

Pack data into a binary string:

<?php
echo pack("C3",80,72,80);
?>

Try it Yourself »

Definition and Usage

The pack() function packs data into a binary string.

Syntax

pack(format,args+)

Parameter Values

Parameter	Description
format	Required. Specifies the format to use when packing data. Possible values: 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-padded string @ - NUL-fill to absolute position
args+	Optional. Specifies one or more arguments to be packed

Parameter

Description

format

Required. Specifies the format to use when packing data.

Possible values:

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-padded string
@ - NUL-fill to absolute position

args+

Optional. Specifies one or more arguments to be packed

Technical Details

Return Value:	Returns data in a binary string
PHP Version:	4+
Changelog:	PHP 7.2 - float and double now supports both big and small endian. PHP 7.0.15 - The "E", "e", "G", "g" code was added. PHP 5.6.3 - The "Q", "q", "J", "P" code was added. PHP 5.5 - The "Z" code was added (holds the same functionality as "a" for Perl compatibility).

More Examples

Example

Pack data into a binary string:

<?php
echo pack("C*",80,72,80);
?>

Try it Yourself »

❮ PHP Misc Reference