The pack() function is an inbuilt function in PHP which is used to pack the given parameter into a binary string in a given format.
Syntax:
pack( $format, $arguments )
Parameters: This function accepts two parameters as mentioned above and described below:
-
$format: It is required parameter. It specifies the format to be used while packing the data. The possible values of format are:
- a – string which is NUL-padded
- A – string which is SPACE-padded
- h – low nibble first Hex string
- H – high nibble first Hex string
- c – signed character
- C – unsigned character
- s – signed short (16 bit, machine byte order)
- S – unsigned short ( 16 bit, machine byte order)
- n – unsigned short ( 16 bit, big endian byte order)
- v – unsigned short ( 16 bit, little endian byte order)
- i – signed integer (machine dependent byte order and size)
- I – unsigned integer (machine dependent byte order and size)
- l – signed long ( 32 bit, machine byte order)
- L – unsigned long ( 32 bit, machine byte order)
- N – unsigned long ( 32 bit, big endian byte order)
- V – unsigned long ( 32 bit, little endian byte order)
- f – float (machine dependent representation and size)
- d – double (machine dependent representation and size)
- x – NUL byte
- X – Back up one byte
- Z – string which is NUL-padded
- @ – NUL-fill to absolute position
- $arguments: It is Optional parameter. It specifies one or more arguments to be packed.
Return Value: It returns a binary string containing data.
Note: This function is available on PHP 4.0.0 and newer version.
Program 1: This program uses C format to format the input parameter.
<?php echo pack("C13", 71, 69, 69, 75, 83, 70, 79, 82, 71, 69, 69, 75, 83);
?> |
Output:
GEEKSFORGEEKS
Program 2: This program uses A format to format the input parameter.
<?php echo pack("A3", 71898);
?> |
Output:
718
Program 3: This program uses i format to format the input parameter.
<?php echo pack("i3", 56, 49, 54);
?> |
Output:
816
Reference: https://www.php.net/manual/en/function.pack.php