PHP | unpack() Function

array unpack( $format, $data, $offset )

• $format: It is required parameter. It specifies the format to be used while packing data.
  • a - denotes string which is NUL-padded.
  • A - denotes string which is SPACE-padded.
  • h - denotes low nibble first Hex string.
  • H - denotes high nibble first Hex string.
  • c - denotes signed character.
  • C - denotes unsigned character.
  • s - denotes signed short (16 bit, machine byte order).
  • S - denotes unsigned short (16 bit, machine byte order).
  • n - denotes unsigned short (16 bit, big endian byte order).
  • v - denotes unsigned short (16 bit, little endian byte order).
  • i - denotes signed integer (machine dependent byte order and size).
  • I - denotes unsigned integer (machine dependent byte order and size).
  • l - denotes signed long (32 bit, machine byte order).
  • L - denotes unsigned long (32 bit, machine byte order).
  • N - denotes unsigned long (32 bit, big endian byte order).
  • V - denotes unsigned long (32 bit, little endian byte order).
  • f - denotes float (machine dependent representation and size).
  • d - denotes double (machine dependent representation and size).
  • x - denotes NUL byte.
  • X - denotes Back up one byte.
  • Z - denotes string which is NUL-padded.
  • @ - denotes NUL-fill to absolute position.
• $data: It is Required parameter. It specifies the binary data to be unpacked.
• offset: This parameter holds the offset to begin from unpacking.

<?php

var_dump( unpack("C*", "GEEKSFORGEEKS"));
?>

array(13) {
  [1]=>
  int(71)
  [2]=>
  int(69)
  [3]=>
  int(69)
  [4]=>
  int(75)
  [5]=>
  int(83)
  [6]=>
  int(70)
  [7]=>
  int(79)
  [8]=>
  int(82)
  [9]=>
  int(71)
  [10]=>
  int(69)
  [11]=>
  int(69)
  [12]=>
  int(75)
  [13]=>
  int(83)
}

<?php

$binary_data = pack("c2n2", 0x1634, 0x3623, 65, 66);
var_dump(unpack("c2chars/n2int", $binary_data));
?>

array(4) {
  ["chars1"]=>
  int(52)
  ["chars2"]=>
  int(35)
  ["int1"]=>
  int(65)
  ["int2"]=>
  int(66)
}

<?php

$binary_data = pack("i3", 56, 49, 54);
var_dump(unpack("i3", $binary_data));
?>

array(3) {
  [1]=>
  int(56)
  [2]=>
  int(49)
  [3]=>
  int(54)
}