php man page for unpack

UNPACK(3)								 1								 UNPACK(3)

unpack - Unpack data from binary string

SYNOPSIS
       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)