Use named regex groups and constants for regex strings

Author: ndench

src/PhpSpreadsheet/Cell/AddressHelper.php

@@ -102,20 +102,20 @@ public static function convertToR1C1(
         ?int $currentRowNumber = null,
         ?int $currentColumnNumber = null
     ): string {
-        $validityCheck = preg_match('/^(\$?)([A-Z]{1,3})(\$?)(\d{1,7})$/i', $address, $cellReference);
+        $validityCheck = preg_match(Coordinate::A1_COORDINATE_REGEX, $address, $cellReference);
 
         if ($validityCheck === 0) {
             throw new Exception('Invalid A1-format Cell Reference');
         }
 
-        $columnId = Coordinate::columnIndexFromString($cellReference[2]);
-        if ($cellReference[1] === '$') {
+        $columnId = Coordinate::columnIndexFromString($cellReference['col_ref']);
+        if ($cellReference['absolute_col'] === '$') {
             // Column must be absolute address
             $currentColumnNumber = null;
         }
 
-        $rowId = (int) $cellReference[4];
-        if ($cellReference[3] === '$') {
+        $rowId = (int) $cellReference['row_ref'];
+        if ($cellReference['absolute_row'] === '$') {
             // Row must be absolute address
             $currentRowNumber = null;
         }

src/PhpSpreadsheet/Cell/Coordinate.php

@@ -13,6 +13,8 @@
  */
 abstract class Coordinate
 {
+    public const A1_COORDINATE_REGEX = '/^(?<absolute_col>\$?)(?<col_ref>[A-Z]{1,3})(?<absolute_row>\$?)(?<row_ref>\d{1,7})$/i';
+
     /**
      * Default range variable constant.
      *
@@ -29,8 +31,8 @@ abstract class Coordinate
      */
     public static function coordinateFromString($pCoordinateString)
     {
-        if (preg_match('/^([$]?[A-Z]{1,3})([$]?\\d{1,7})$/', $pCoordinateString, $matches)) {
-            return [$matches[1], $matches[2]];
+        if (preg_match(self::A1_COORDINATE_REGEX, $pCoordinateString, $matches)) {
+            return [$matches['absolute_col'] . $matches['col_ref'], $matches['absolute_row'] . $matches['row_ref']];
         } elseif (self::coordinateIsRange($pCoordinateString)) {
             throw new Exception('Cell coordinate string can not be a range of cells');
         } elseif ($pCoordinateString == '') {