How to convert hexadecimal string to byte array in php

In PHP programming, byte arrays (byte arrays) are often used data types, and hexadecimal strings are often used to represent binary data. The process of converting a hexadecimal string into a byte array is a problem we often encounter when processing binary data. In this article, we will discuss how to convert a hexadecimal string into a byte array in PHP.

1. Understanding hexadecimal strings

In computers, binary numbers are the most basic data type, but writing binary numbers is very cumbersome. In order to facilitate writing and reading, we usually convert binary numbers into hexadecimal numbers to facilitate distinction and identification when writing and reading. Hexadecimal numbers can be directly represented by ASCII characters, such as 0x1A, 0xFF, 0x2B, etc.

Hexadecimal numbers can be easily converted into binary numbers. For example, 0x1A is represented as 0001 1010, and 0xFF is represented as 1111 1111. When we transmit data to the computer, we often need to convert the data into binary bits and then transmit it. However, it is inconvenient for us to write binary data directly in the code, so binary numbers are often expressed as hexadecimal strings for transmission.

2. Methods to convert hexadecimal strings into byte arrays

In PHP, there are many ways to convert hexadecimal strings into byte arrays, as follows We will introduce two of them:

2.1 Using the pack and hexdec functions

The pack function can load the values ​​​​in an array into a binary string according to the specified format, and the hexdec function can load a 16 Convert hexadecimal strings into decimal numbers.

The specific operation steps are as follows:

$hex_str = "12AB34CD";
$len = strlen($hex_str);
$ret = array();
for ($i=0; $i<$len; $i+=2) { 
  array_push($ret, hexdec(substr($hex_str, $i, 2)));
}

The above code uses every two characters as a hexadecimal number through a loop, and then converts the hexadecimal string into decimal through the hexdec function. and stored in byte array.

2.2 Using bin2hex and unpack functions

The bin2hex function can convert a binary string into a hexadecimal string, and the unpack function can convert a binary string into an array.

The specific operation steps are as follows:

$hex_str = "12AB34CD";
$bin_str = hex2bin($hex_str);
$ret = unpack("C*", $bin_str);

The above code converts the hexadecimal string into a binary string through the hex2bin function, and then converts the binary string into a byte array through the unpack function.

3. Summary

Both of the above two methods can convert hexadecimal strings into byte arrays. Which method to choose can be considered based on actual needs and memory overhead. . In practical applications, we need to use byte arrays for binary data processing, which are widely used in scenarios such as parsing non-text files and network transmission of binary files.

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