UNPACK(3) 1 UNPACK(3)unpack - Unpack data from binary stringSYNOPSIS
array unpack (string $format, string $data)
DESCRIPTION
Unpacks from a binary string into an array according to the given $format.
The unpacked data is stored in an associative array. To accomplish this you have to name the different format codes and separate them by a
slash /. If a repeater argument is present, then each of the array keys will have a sequence number behind the given name.
PARAMETERS
o $format
- See pack(3) for an explanation of the format codes.
o $data
- The packed data.
RETURN VALUES
Returns an associative array containing unpacked elements of binary string.
CHANGELOG
+--------+---------------------------------------------------+
|Version | |
| | |
| | Description |
| | |
+--------+---------------------------------------------------+
| 5.5.0 | |
| | |
| | Changes were made to bring this function into |
| | line with Perl: The "a" code now retains trail- |
| | ing NULL bytes. The "A" code now strips all |
| | trailing ASCII whitespace (spaces, tabs, new- |
| | lines, carriage returns, and NULL bytes). The |
| | "Z" code was added for NULL-padded strings, and |
| | removes trailing NULL bytes. |
| | |
+--------+---------------------------------------------------+
EXAMPLES
Example #1
unpack(3) example
<?php
$binarydata = "x04x00xa0x00";
$array = unpack("cchars/nint", $binarydata);
?>
The resulting array will contain the entries "chars" with value 4 and "int" with 160.
Example #2
unpack(3) example with a repeater
<?php
$binarydata = "x04x00xa0x00";
$array = unpack("c2chars/nint", $binarydata);
?>
The resulting array will contain the entries "chars1", "chars2" and "int".
NOTES
Caution
Note that PHP internally stores integral values as signed. If you unpack a large unsigned long and it is of the same size as PHP
internally stored values the result will be a negative number even though unsigned unpacking was specified.
Caution
Be aware that if you do not name an element, an empty string is used. If you do not name more than one element, this means that
some data is overwritten as the keys are the same such as in:
Example #3
unpack(3) example with unnamed keys
<?php
$binarydata = "x32x42x00xa0";
$array = unpack("c2/n", $binarydata);
var_dump($array);
?>
The resulting array will contain the entries "1" with value 160 and "2" with 66. The first value from the c specifier is
overwritten by the first value from the n specifier.
SEE ALSO pack(3).
PHP Documentation Group UNPACK(3)
Check Out this Related Man Page
PACK(3) 1 PACK(3)pack - Pack data into binary stringSYNOPSIS
string pack (string $format, [mixed $args], [mixed $...])
DESCRIPTION
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 Perl's "u" format code.
Note that the distinction between signed and unsigned values only affects the function unpack(3), where as function pack(3) gives the same
result for signed and unsigned format codes.
PARAMETERS
o $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(3) format characters
+-----+---------------------------------------------------+
|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) |
| | |
| d | |
| | |
| | double (machine dependent size and representa- |
| | tion) |
| | |
| x | |
| | |
| | NUL byte |
| | |
| X | |
| | |
| | Back up one byte |
| | |
| Z | |
| | |
| | NUL-padded string (new in PHP 5.5) |
| | |
| @ | |
| | |
| | NUL-fill to absolute position |
| | |
+-----+---------------------------------------------------+
o $args
-
RETURN VALUES
Returns a binary string containing data.
CHANGELOG
+--------+---------------------------------------------------+
|Version | |
| | |
| | Description |
| | |
+--------+---------------------------------------------------+
| 5.6.3 | |
| | |
| | The "q", "Q", "J" and "P" codes were added to |
| | enable working with 64-bit numbers. |
| | |
| 5.5.0 | |
| | |
| | The "Z" code was added with equivalent function- |
| | ality to "a" for Perl compatibility. |
| | |
+--------+---------------------------------------------------+
EXAMPLES
Example #1
pack(3) example
<?php
$binarydata = pack("nvc*", 0x1234, 0x5678, 65, 66);
?>
The resulting binary string will be 6 bytes long and contain the byte sequence 0x12, 0x34, 0x78, 0x56, 0x41, 0x42.
NOTES
Caution
Note that PHP internally stores integer values as signed values of a machine-dependent size (C type long). Integer literals and
operations that yield numbers outside the bounds of the integer type will be stored as float. When packing these floats as integers,
they are first cast into the integer type. This may or may not result in the desired byte pattern.
The most relevant case is when packing unsigned numbers that would be representable with the integer type if it were unsigned. In
systems where the integer type has a 32-bit size, the cast usually results in the same byte pattern as if the integer were unsigned
(although this relies on implementation-defined unsigned to signed conversions, as per the C standard). In systems where the integer
type has 64-bit size, the float most likely does not have a mantissa large enough to hold the value without loss of precision. If
those systems also have a native 64-bit C int type (most UNIX-like systems don't), the only way to use the I pack format in the
upper range is to create integer negative values with the same byte representation as the desired unsigned value.
SEE ALSO unpack(3).
PHP Documentation Group PACK(3)