PHP pack() Function
The PHP pack() function packs data 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: 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.
Syntax
pack(format, values)
Parameters
format |
Required. Specify 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. The repeat count specifies the following:
|
values |
Required. Specify the data that need to be packed. Multiple parameters are allowed. |
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) |
| 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 |
Return Value
Returns a binary string containing data, or false on failure.
Example: pack() example
The example below shows the usage of pack() function.
<?php
echo pack("C3",80,72,80);
?>
The output of the above code will be:
PHP
Example: another pack() example
Consider one more example where the usage of this function is discussed.
<?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.
❮ PHP Miscellaneous Reference
