   #PHP Manual Miscellaneous functions ignore_user_abort show_source

   PHP Manual
   Prev  Next
   ______________________________________________________________________

                                     pack

   (PHP 3, PHP 4 )
   pack -- Pack data into binary string.

Description

   string pack ( string format [, mixed args])

   Pack given arguments into binary string according to format. Returns
   binary string containing data.

   The idea to this function was taken from Perl and all formatting codes
   work the same as there, however, there are some formatting codes that
   are missing such as Perl's "u" format code. 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 are

   Table 1. pack() 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)
   f    float (machine dependent size and representation)
   d    double (machine dependent size and representation)
   x    NUL byte
   X    Back up one byte
   @    NUL-fill to absolute position

   Example 1. pack() 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.

   Note that the distinction between signed and unsigned values only
   affects the function unpack(), where as function pack() gives the same
   result for signed and unsigned format codes.

   Also note that PHP internally stores integer values as signed values
   of a machine dependent size. If you give it an unsigned integer value
   too large to be stored that way it is converted to a float which often
   yields an undesired result.
   ______________________________________________________________________

   Prev              Home        Next
   ignore_user_abort  Up  show_source
