framework/log/FileTarget.php
private function rotateByCopy($rotateFile, $newFile)
    {
        @copy($rotateFile, $newFile);
        if ($this->fileMode !== null) {
            @chmod($newFile, $this->fileMode);
        }
    }
private function rotateByCopy($rotateFile, $newFile)
    {
        @copy($rotateFile, $newFile);
        if ($this->fileMode !== null) {
            @chmod($newFile, $this->fileMode);
        }
    }
*
Copy rotated file into new file
@param string $rotateFile
@param string $newFile