<?php
// Define the string to convert into QR code
$string = "This is another random string for QR code example";

// Define the size of the QR code in pixels
$size = 200;

// Define the error correction level of the QR code
// Possible values are L (7%), M (15%), Q (25%), H (30%)
$level = "M";

// Define the margin of the QR code in pixels
$margin = 4;

// Define the number of bits per pixel
$bits = 8;

// Define the character set to use for encoding the string
$charset = "ISO-8859-1";

// Define the function to convert a string into a binary array
function str2bin($str, $charset)
{
    // Convert the string to the specified character set
    $str = iconv("UTF-8", $charset, $str);
    // Initialize an empty array to store the binary data
    $bin = array();
    // Loop through each character in the string
    for ($i = 0; $i < strlen($str); $i++) {
        // Get the ASCII code of the character
        $ord = ord($str[$i]);
        // Convert the ASCII code into a binary string of 8 bits
        $binstr = decbin($ord);
        $binstr = str_pad($binstr, 8, "0", STR_PAD_LEFT);
        // Split the binary string into an array of bits
        $binarr = str_split($binstr);
        // Append the array of bits to the binary data array
        $bin = array_merge($bin, $binarr);
    }
    // Return the binary data array
    return $bin;
}

// Define the function to convert a binary array into a string
function bin2str($bin, $charset)
{
    // Initialize an empty string to store the decoded data
    $str = "";
    // Loop through the binary array in chunks of 8 bits
    for ($i = 0; $i < count($bin); $i += 8) {
        // Get a slice of 8 bits from the binary array
        $binarr = array_slice($bin, $i, 8);
        // Join the bits into a binary string
        $binstr = implode("", $binarr);
        // Convert the binary string into an ASCII code
        $ord = bindec($binstr);
        // Convert the ASCII code into a character
        $chr = chr($ord);
        // Append the character to the decoded data string
        $str .= $chr;
    }
    // Convert the string to UTF-8 character set
    $str = iconv($charset, "UTF-8", $str);
    // Return the decoded data string
    return $str;
}

// Define the function to generate a QR code matrix from a binary array
function genQR($bin, $size, $level, $margin)
{
    // Define the error correction codewords for each level and version
    $ecc = array(
        "L" => array(7, 10, 15, 20),
        "M" => array(10, 16, 26, 36),
        "Q" => array(13, 22, 36, 52),
        "H" => array(17, 28, 44, 64)
    );
    // Define the alignment pattern positions for each version
    $align = array(
        array(),
        array(6, 18),
        array(6, 22),
        array(6, 26),
        array(6, 30)
    );
    // Define the version of the QR code based on the size
    $version = ($size - 21) / 4 + 1;
    // Define the data codewords for the version and level
    $data = $size * $size - 64 - 3 * 25 - 2 * ($margin + 7) * ($size - 2 * $margin) - $ecc[$level][$version - 1];
    // Define the total codewords for the version
    $total = $size * $size / 8;
    // Check if the binary data fits in the QR code
if (count($bin) > $data) {
    // Return an error message
    return "The data is too long for this QR code";
}
// Pad the binary data with 0s until it reaches the data codewords
while (count($bin) < $data) {
    $bin[] = 0;
}
// Add the error correction codewords to the binary data
for ($i = 0; $i < $ecc[$level][$version - 1]; $i++) {
    // Check if the key exists in the array
    if (isset($bin[$i])) {
        // Append the value to the binary data
        $bin[] = $bin[$i];
    }
    else {
        // Return an error message
        return "The key $i is undefined";
    }
}

    // Check if the binary data matches the total codewords
    if (count($bin) != $total) {
        // Return an error message
        return "The data is corrupted";
    }
    // Initialize an empty array to store the QR code matrix
    $qr = array();
    // Loop through the rows of the QR code matrix
    for ($i = 0; $i < $size; $i++) {
        // Initialize an empty array to store the row
        $row = array();
        // Loop through the columns of the QR code matrix
        for ($j = 0; $j < $size; $j++) {
            // Initialize the pixel value to null
            $pixel = null;
            // Check if the pixel is in the margin area
            if ($i < $margin || $i >= $size - $margin || $j < $margin || $j >= $size - $margin) {
                // Set the pixel value to 0 (white)
                $pixel = 0;
            }
            // Check if the pixel is in the finder pattern area
            elseif ($i < $margin + 7 && $j < $margin + 7 || $i < $margin + 7 && $j >= $size - $margin - 7 || $i >= $size - $margin - 7 && $j < $margin + 7) {
                // Set the pixel value according to the finder pattern
                $pixel = ($i + $j) % 2 == 0 || $i == $margin + 3 || $j == $margin + 3 ? 1 : 0;
            }
            // Check if the pixel is in the separator area
            elseif ($i == $margin || $i == $margin + 6 || $i == $size - $margin - 1 || $i == $size - $margin - 7 || $j == $margin || $j == $margin + 6 || $j == $size - $margin - 1 || $j == $size - $margin - 7) {
                // Set the pixel value to 0 (white)
                $pixel = 0;
            }
            // Check if the pixel is in the alignment pattern area
            elseif (in_array($i, $align[$version - 1]) && in_array($j, $align[$version - 1])) {
                // Set the pixel value according to the alignment pattern
                $pixel = ($i + $j) % 2 == 0 || abs($i - $j) == 2 ? 1 : 0;
            }
            // Check if the pixel is in the timing pattern area
            elseif ($i == $margin + 6 || $j == $margin + 6) {
                // Set the pixel value according to the timing pattern
                $pixel = ($i + $j) % 2 == 0 ? 1 : 0;
            }
            // Check if the pixel is in the format information area
            elseif ($i == $margin + 8 || $j == $margin + 8) {
                // Set the pixel value to null
                $pixel = null;
            }
            // Check if the pixel is in the version information area
            elseif ($version >= 2 && $version <= 5 && ($i >= $size - $margin - 11 && $i <= $size - $margin - 9 && $j < $margin + 6 || $j >= $size - $margin - 11 && $j <= $size - $margin - 9 && $i < $margin + 6)) {
                // Set the pixel value to null
                $pixel = null;
            }
            // Check if the pixel is in the data area
            else {
                // Set the pixel value to the next bit in the binary data
                $pixel = array_shift($bin);
            }
            // Append the pixel value to the row
            $row[] = $pixel;
        }
        // Append the row to the QR code matrix
        $qr[] = $row;
    }
    // Return the QR code matrix
    return $qr;
}

// Define the function to display a QR code matrix as an image
function showQR($qr, $size, $bits)
{
    // Check if the QR code matrix is valid
    if (is_array($qr) && count($qr) == $size && count($qr[0]) == $size) {
        // Create a new image resource with the specified size and bits
        $img = imagecreatetruecolor($size, $size);
        // Allocate the colors for the image
        $white = imagecolorallocate($img, 255, 255, 255);
        $black = imagecolorallocate($img, 0, 0, 0);
        // Loop through the rows of the QR code matrix
        for ($i = 0; $i < $size; $i++) {
            // Loop through the columns of the QR code matrix
            for ($j = 0; $j < $size; $j++) {
                // Get the pixel value from the QR code matrix
                $pixel = $qr[$i][$j];
                // Check if the pixel value is 0 (white) or 1 (black)
                if ($pixel == 0 || $pixel == 1) {
                    // Set the color of the pixel in the image
                    $color = $pixel == 0 ? $white : $black;
                    imagesetpixel($img, $j, $i, $color);
                }
            }
        }
        // Output the image as a PNG file
        header("Content-Type: image/png");
        imagepng($img);
        // Destroy the image resource
        imagedestroy($img);
    } else {
        // Return an error message
        return "The QR code matrix is invalid";
    }
}

// Convert the string into a binary array
$bin = str2bin($string, $charset);

// Generate a QR code matrix from the binary array
$qr = genQR($bin, $size, $level, $margin);

// Display the QR code matrix as an image
showQR($qr, $size, $bits);
