A script for generating sparklines in PHP. See https://www.hashbangcode.com/article/creating-sparklines-php for more information.

sparkline.php

<?php
/**
 * A script for generating sparklines in PHP.
 *
 * To use this script, create an image tag and pass a data parameter to it.
 * <code>
 *     <img src="/sparkline.php?&data=10,40,20,10,0,20,40,50,100,20"/><br>
 * </code>
 *
 * You can also alter the width and height of the chart by passing w and h.
 * <code>
 *     <img src="/sparkline.php?w=150&h=20&data=10,40,20,10,0,20,40,50,100,20"/><br>
 * </code>
 *
 * @author Philip Norton (https://github.com/philipnorton42)
 * @see https://www.hashbangcode.com/article/creating-sparklines-php
 */

// Process the passed data.
$data = [];
if (isset($_GET['data']) && str_contains($_GET['data'], ',')) {
    foreach (explode(',', $_GET['data']) as $datum) {
        if (is_numeric($datum)) {
            // Ignore anything that that isn't a number.
            $data[] = $datum;
        }
    }
}

// Define the width.
$width = 50;
if (isset($_GET['w']) && is_numeric($_GET['w']) && $_GET['w'] < 300) {
    // Set the passed width, cast to an integer.
    $width = (int) $_GET['w'];
}

// Define the height.
$height = 30;
if (isset($_GET['h']) && is_numeric($_GET['h']) && $_GET['h'] < 300) {
    // Set the passed height, cast to an integer.
    $height = (int) $_GET['h'];
}

// Create the image.
$image = imagecreatetruecolor($width, $height);

// Set the background colour.
$backgroundColour = imagecolorallocate($image, 255, 255, 255);
imagefilledrectangle($image, 0, 0, $width, $height, $backgroundColour);

if (empty($data)) {
    // If the $data is empty then output a blank image.
    header('Content-Type: image/png');
    imagepng($image);
    exit();
}

// Set the line colours.
$lineColour = imagecolorallocate($image, 0, 0, 255);
$baseLineColour = imagecolorallocate($image, 128, 128, 128);

// Now that we have defined the height of the image ensure 0 on the chart is
// actually 1.
$height--;

// Get the maximum value from the data.
$maxValue = max($data);
$minValue = min($data);

if ($minValue < 0 && $maxValue > 0) {
    // This line crosses the 0 point, so draw the base line of the chart at 0.
    $x1 = 0;
    $x2 = $width;
    $y1 = $height - round($height * ((0 - $minValue) / ($maxValue - $minValue)));
    $y2 = $height - round($height * ((0 - $minValue) / ($maxValue - $minValue)));
    imageline($image, $x1, $y1, $x2, $y2, $baseLineColour);
}

// Calculate the corrected distance between each point in the chart.
$barWidth = ($width) / (count($data) -1);

// Draw the line of the chart.
for ($i = 0; $i < count($data) -1; $i++) {
    $value = $data[$i] ?? 0;
    $nextValue = $data[$i + 1] ?? 0;
    $x1 = floor($i * $barWidth);
    $x2 = floor($x1 + $barWidth - 1);
    $y1 = $height - round($height * (($value - $minValue) / ($maxValue - $minValue)));
    $y2 = $height - round($height * (($nextValue - $minValue) / ($maxValue - $minValue)));

    imageline($image, $x1, $y1, $x2, $y2, $lineColour);
}

// Output image.
header('Content-Type: image/png');
imagepng($image);

unset($data);