Less/SCSS files which are combined are incorrectly calculated by Contao: Changes in sub-Files are not recognized. This script checks the filetime of the sub-Files in the folder and corrects the filetime of the parent app.less/scss
Therefore, the checkmodified.php is placed into the main less/scss directory (e.g., files/layout/scss/) where also the app.less/scss file lies.
Then, a line with the correct (relative or absolute) path to checkmodified.php is added in system/config/initconfig.php to process this file on every page load during Contao initialization:
// Check if we have modified sub-less/scss-files. If so, modify the parent less/scss-file so that a new complete less/scss.css-file can be generated
$checkmodified = "../files/layout/scss/checkmodified.php"; if (file_exists($checkmodified)) include_once($checkmodified);