doc/dev/plugins/admin/classes/plugin/ScssCompiler.php

<?php
namespace Grav\Plugin\Admin;

use ScssPhp\ScssPhp\Compiler;

class ScssCompiler
{
    protected $compiler;

    public function compiler()
    {
        if ($this->compiler === null) {
            $this->reset();
        }
        return $this->compiler;
    }

    public function reset()
    {
        $this->compiler = new Compiler();
        return $this;
    }

    public function setVariables(array $variables)
    {
        $this->compiler()->setVariables($variables);
        return $this;
    }

    public function setImportPaths(array $paths)
    {
        $this->compiler()->setImportPaths($paths);
        return $this;
    }

    public function compile(string $input_file, string $output_file)
    {
        $input = file_get_contents($input_file);
        $output = $this->compiler()->compile($input);
        file_put_contents($output_file, $output);
        return $this;
    }

    public function compileAll(array $input_paths, string $output_file)
    {
        $input = '';
        foreach ($input_paths as $input_file) {
            $input .= trim(file_get_contents($input_file)) . "\n\n";
        }
        $output = $this->compiler()->compile($input);
        file_put_contents($output_file, $output);
        return $this;
    }

}