Combined with str_split to implement CRC checking of strings

M66 2025-05-28

When processing data verification, CRC (cyclic redundancy verification) is a common verification method. CRC verification is usually used to verify that data has changed during transmission. In this article, we will discuss how to use PHP's str_split function in conjunction with a simple CRC check algorithm to achieve this function.

What is CRC verification?

CRC verification is an algorithm used to verify data integrity. It generates a "check code" (usually a number) by performing specific mathematical operations on the data. The receiver can use the same algorithm to recalculate the check code. If the calculated value is consistent with the transmitted check code, it means that there is no error in the data.

In practical applications, CRC verification is generally used in file transfer, network protocol and other scenarios to ensure the integrity of data transmission.

Combined with PHP's str_split function to implement CRC verification

The str_split function in PHP can split a string into multiple substrings. When doing CRC checks, we can use it to break the input string into smaller parts for calculation. Here is a simple implementation.

1. Define the CRC check function

We can define a simple CRC check function, using bit operations and str_split function to implement data checking.

 <?php
function crc_check($data) {
    $crc = 0xFFFF; // initialization CRC value
    $dataArray = str_split($data); // Split the data string into a character array
    
    foreach ($dataArray as $char) {
        $byte = ord($char); // Get characters ASCII value
        $crc ^= $byte; // Will CRC Exclusive OR operation with the current byte

        // right CRC valueconduct位移处理
        for ($i = 0; $i < 8; $i++) {
            if ($crc & 0x0001) {
                $crc >>= 1;
                $crc ^= 0xA001; // If the lowest position is1，conduct XOR operate
            } else {
                $crc >>= 1;
            }
        }
    }

    return strtoupper(dechex($crc)); // Return to hexadecimal CRC value
}

// Sample data
$data = "Hello, world!";
// Call CRC Verification function
$crcResult = crc_check($data);
echo "CRC Verification results: " . $crcResult;
?>

2. Code explanation

str_split($data) : Split the input data $data into a single character array.
ord($char) : Returns the ASCII value of the character.
Bit operation part: The core part of the CRC algorithm is implemented through XOR operation and displacement calculation. This process processes each byte and generates the final CRC check value through a series of XOR and displacement operations.
dechex($crc) : converts the final CRC check value into a hexadecimal representation.

Through the above steps, we can get the CRC check code of the input string.

3. Use case demonstration

If we perform CRC verification on the string "Hello, world!", the code will return a CRC verification code. Assume that the return value is E8B7BE43 .

 $crcResult = crc_check("Hello, world!");
echo "CRC Verification results: " . $crcResult;

summary

By combining PHP's str_split function with CRC verification algorithm, we can simply implement integrity verification of strings. The str_split function helps us break down strings into single characters, which allows us to perform CRC calculations byte byte.

Hope this article can help you better understand how to implement CRC verification using PHP. If you have more questions, feel free to ask!

str_split