Documentation Update

Author: oleibman

docs/topics/accessing-cells.md

@@ -42,6 +42,19 @@ $spreadsheet->getActiveSheet()
 If you make a call to `getCell()`, and the cell doesn't already exist, then
 PhpSpreadsheet will create that cell for you.
 
+### Copying a Cell's Value And Style Adjusting Formulas
+
+If cell A1 contains `5`, cell A2 contains `10`, and cell `B1` contains `=A1`, the formula in B1 will be evaluated as `5`. In Excel, if you copy B1 to B2, B2 will wind up with the adjusted formula `=A2` and will be evaluated as 10. Until release 5.1.0, PhpSpreadsheet requires the program to perform its own formula adjustment. In 5.1.0, a new method is introduced to handle formula adjustments:
+```php
+$worksheet->copyformula($fromCell, $toCell);
+```
+This will behave as Excel does. If $fromCell does not contain a formula, its contents will be copied as-is.
+
+If you also want to copy $fromCell's style, as Excel does, you can use the following (available in all supported releases):
+```php
+$worksheet->duplicateStyle($fromCell->getStyle(), $toCell);
+```
+
 ### BEWARE: Cells and Styles assigned to variables as a Detached Reference
 
 As an "in-memory" model, PHPSpreadsheet can be very demanding of memory,