PHPOffice / PhpSpreadsheet

                            //    Convert R1C1 style references to A1 style references (but only when not quoted)

                            $temp = explode('"', $cellDataFormula);

                            $key = false;

                            foreach ($temp as &$value) {

                                //    Only count/replace in alternate array entries

                                if ($key = !$key) {

                                    preg_match_all('/(R(\[?-?\d*\]?))(C(\[?-?\d*\]?))/', $value, $cellReferences, PREG_SET_ORDER + PREG_OFFSET_CAPTURE);

                                    //    Reverse the matches array, otherwise all our offsets will become incorrect if we modify our way

                                    //        through the formula from left to right. Reversing means that we work right to left.through

                                    //        the formula

                                    $cellReferences = array_reverse($cellReferences);

                                    //    Loop through each R1C1 style reference in turn, converting it to its A1 style equivalent,

                                    //        then modify the formula to use that new reference

                                    foreach ($cellReferences as $cellReference) {

                                        $rowReference = $cellReference[2][0];

                                        //    Empty R reference is the current row

                                        if ($rowReference == '') {

                                            $rowReference = $row;

                                        }

                                        //    Bracketed R references are relative to the current row

                                        if ($rowReference[0] == '[') {

                                            $rowReference = $row + trim($rowReference, '[]');

                                        }

                                        $columnReference = $cellReference[4][0];

                                        //    Empty C reference is the current column

                                        if ($columnReference == '') {

                                            $columnReference = $column;

                                        }

                                        //    Bracketed C references are relative to the current column

                                        if ($columnReference[0] == '[') {

                                            $columnReference = $column + trim($columnReference, '[]');

                                        }

                                        $A1CellReference = \PhpOffice\PhpSpreadsheet\Cell::stringFromColumnIndex($columnReference - 1) . $rowReference;

                                        $value = substr_replace($value, $A1CellReference, $cellReference[0][1], strlen($cellReference[0][0]));

                                    }

                                }

                            }

                            unset($value);

                            //    Then rebuild the formula string

                                    //    Convert R1C1 style references to A1 style references (but only when not quoted)

                                    $temp = explode('"', $cellDataFormula);

                                    $key = false;

                                    foreach ($temp as &$value) {

                                        //    Only replace in alternate array entries (i.e. non-quoted blocks)

                                        if ($key = !$key) {

                                            preg_match_all('/(R(\[?-?\d*\]?))(C(\[?-?\d*\]?))/', $value, $cellReferences, PREG_SET_ORDER + PREG_OFFSET_CAPTURE);

                                            //    Reverse the matches array, otherwise all our offsets will become incorrect if we modify our way

                                            //        through the formula from left to right. Reversing means that we work right to left.through

                                            //        the formula

                                            $cellReferences = array_reverse($cellReferences);

                                            //    Loop through each R1C1 style reference in turn, converting it to its A1 style equivalent,

                                            //        then modify the formula to use that new reference

                                            foreach ($cellReferences as $cellReference) {

                                                $rowReference = $cellReference[2][0];

                                                //    Empty R reference is the current row

                                                if ($rowReference == '') {

                                                    $rowReference = $rowID;

                                                }

                                                //    Bracketed R references are relative to the current row

                                                if ($rowReference[0] == '[') {

                                                    $rowReference = $rowID + trim($rowReference, '[]');

                                                }

                                                $columnReference = $cellReference[4][0];

                                                //    Empty C reference is the current column

                                                if ($columnReference == '') {

                                                    $columnReference = $columnNumber;

                                                }

                                                //    Bracketed C references are relative to the current column

                                                if ($columnReference[0] == '[') {

                                                    $columnReference = $columnNumber + trim($columnReference, '[]');

                                                }

                                                $A1CellReference = \PhpOffice\PhpSpreadsheet\Cell::stringFromColumnIndex($columnReference - 1) . $rowReference;

                                                $value = substr_replace($value, $A1CellReference, $cellReference[0][1], strlen($cellReference[0][0]));

                                            }

                                        }

                                    }

                                }

                                unset($value);

                                //    Then rebuild the formula string

                                $cellDataFormula = implode('"', $temp);