ExcelExtension.php

<?php
namespace AppBundle\Twig\Extension;


/**
 * A TWIG Extension which allows to generate a range of excel columns
 * Since excel works with column names instead of numbers a range of names is needed.
 */
class ExcelExtension extends \Twig_Extension
{
    public function getFunctions()
    {
        return [
            new \Twig_SimpleFunction('excelColumnNames', [$this, 'excelColumnNames']),
        ];
    }

    /**
     * @param $start The name of the start column e.g. 'D', optional default is 'A'
     * @param null|int|string $length Either the length of the range e.g. 7 or the name of the last column name e.g. 'J'
     * @return \Generator
     */
    public function excelColumnNames($start, $length=null)
    {
        if (is_null($length))
        {
            $length = $start;
            $start = 'A';
        }
        $i = 0;
        if (!is_int($length)) { $length++; }
        while (
            (is_int($length) && $i < $length) ||
            (!is_int($length) && $start != $length) // Since in PHP 'AC' < 'D' we cannot use the lesser than operator.
                                                    // So no protection against an end column smaller than start.
        ) {
            yield $start;
            $i++;
            $start++;
        }
    }
}