Taken from: https://github.com/PHPOffice/PhpSpreadsheet/blob/master/src/PhpSpreadsheet/Cell/Coordinate.php
public static function stringFromColumnIndex($columnIndex)
{
static $indexCache = [];
if (!isset($indexCache[$columnIndex])) {
$indexValue = $columnIndex;
$base26 = null;
do {
$characterValue = ($indexValue % 26) ?: 26;
$indexValue = ($indexValue - $characterValue) / 26;
$base26 = chr($characterValue + 64) . ($base26 ?: '');
} while ($indexValue > 0);
$indexCache[$columnIndex] = $base26;
}
return $indexCache[$columnIndex];
}
stringFromColumnIndex(28)
return 'AB'