private function getChangedAt(string $filename) : float
    {
        clearstatcache(true, $filename);

        return file_exists($filename)
            ? (float) file_get_contents($filename)
            : -1;
    }
private function getChangedAt(string $filename) : float
    {
        clearstatcache(true, $filename);

        return file_exists($filename)
            ? (float) file_get_contents($filename)
            : -1;
    }
private function getChangedAt ( string $ filename ) : float { clearstatcache ( true , $ filename ) ; return file_exists ( $ filename ) ? ( float ) file_get_contents ( $ filename ) : - 1 ; }
Get the content of a file as a timestamp.

Reading the timestamp from a file is much more reliable than filemtime.
Especially on virtual machine shared folders due to the lag in updating the file stats on the client machine.

@param string $filename

@return float
Get the content of a file as a timestamp .