How to convert binary data to byte array in php

In development, we often need to transmit data in binary form. At this time, we need to convert the binary data into a byte array so that the data can be transmitted more stably and efficiently during the transmission process. In PHP, the way to achieve this function is through the pack function and unpack function. Let's learn about it together.

1. pack function

The pack function is a binary data packaging function in PHP. It can pack the specified data into a binary string according to the specified format. Among them, the format string parameters are specified according to the byte order to be packed, and each format character corresponds to a data type. The following is the basic usage of the pack function:

string pack ( string $format [, mixed $args [, mixed $... ]] )

Among them, the $format parameter is the format string, and $args is the data that needs to be packed.

The following is an example to illustrate the use of the pack function:

$binary_str = pack("C*", 67, 119, 105, 107, 105); echo $binary_str;

In this example, the format string "C*" means packaging by character, and the args parameters are 67, 119, 105, 107,105. The execution result is:

Cwiki

That is, the string composed of the character array 67, 119, 105, 107, 105 is packed in character mode and the string "Cwiki" is returned.

In addition to character mode, the pack function also supports various other packing modes, such as integer (I), long integer (L), double precision (d), etc. The following are some commonly used format characters:

• a: null-terminated string
• A: space-filled string
• 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)

2. unpack function

The unpack function is a binary data unpacking function in PHP. It can unpack binary data strings into specified data types. Like the pack function, we can unpack binary data into variables representing different data types by specifying format string parameters and data strings. The following is the basic usage of the unpacking function:

array unpack ( string $format , string $data )

Among them, the $format parameter is the format string, and $data is the data that needs to be unpacked.

The following is an example to illustrate the use of the unpack function:

$binary_str = "Cwiki"; $unpacked = unpack("C*",$binary_str); print_r($unpacked);

In this example, $binary_str is the binary data string "Cwiki", and the $format parameter is "C*", which means press Character mode unpacking. The execution result is:

Array ( [1] => 67 [2] => 119 [3] => 105 [4] => 107 [5] => 105 )

That is, the binary data string "Cwiki" is unpacked in character mode and an array representing different characters is obtained.

In addition to the character method, the unpack function also supports a variety of other unpacking methods, and the correspondence between the format characters and the format characters of the pack function is one-to-one.

To sum up, through the combined use of the pack function and the unpack function, we can convert any data into a binary string and unpack various data types from the binary string, thereby realizing PHP binary Function to convert to byte array.

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