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<?php
namespace Box\Spout\Writer\Common\Helper;
/**
* Class CellHelper
* This class provides helper functions when working with cells
*/
class CellHelper
{
/** @var array Cache containing the mapping column index => cell index */
private static $columnIndexToCellIndexCache = [];
/**
* Returns the cell index (base 26) associated to the base 10 column index.
* Excel uses A to Z letters for column indexing, where A is the 1st column,
* Z is the 26th and AA is the 27th.
* The mapping is zero based, so that 0 maps to A, B maps to 1, Z to 25 and AA to 26.
*
* @param int $columnIndex The Excel column index (0, 42, ...)
* @return string The associated cell index ('A', 'BC', ...)
*/
public static function getCellIndexFromColumnIndex($columnIndex)
{
$originalColumnIndex = $columnIndex;
// Using isset here because it is way faster than array_key_exists...
if (!isset(self::$columnIndexToCellIndexCache[$originalColumnIndex])) {
$cellIndex = '';
$capitalAAsciiValue = ord('A');
do {
$modulus = $columnIndex % 26;
$cellIndex = chr($capitalAAsciiValue + $modulus) . $cellIndex;
// substracting 1 because it's zero-based
$columnIndex = (int) ($columnIndex / 26) - 1;
} while ($columnIndex >= 0);
self::$columnIndexToCellIndexCache[$originalColumnIndex] = $cellIndex;
}
return self::$columnIndexToCellIndexCache[$originalColumnIndex];
}
}