this is just a php version of the original code at
https://weber.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf
composer require blackscorp/simplexnoise
$noise2D = new \BlackScorp\SimplexNoise\Noise2D();
$greyValue = $noise2D->getGreyValue($locationX, $locationY);
var_dump($greyValue); //a value between 0 and 255
for more examples and details please take a look at examples folder. just copy more png images into exampels/gradients in order to create cool effects
currently only 2D is implemented