Creates an Excel column label from an integer

column_label.function.php

<?php

/**
 * Creates an Excel column label from an integer where 0 = A,
 * 25 = Z, 26 = AA and so on.
 *
 * Examples:
 * <code>
 * <?php
 * echo column_label(0); // A
 * echo column_label(25); // Z
 * echo column_label(26); // AA
 * echo column_label(702); // AAA
 * ?>
 * </code>
 *
 * @author  Felds Liscia <dev@felds.com.br>
 * @param   integer $pos    The column index
 * @return  string  The label
 */
function column_label($pos)
{
    // normalizes the input
    $pos = (int) $pos;

    // generating an array of letters like [A, B, C, ..Z] 
    static $letters;
    if (! $letters) $letters = range('A', 'Z');

    // if the column index is equal or larger than 26 (# of letters from A~Z) ...
    if ($pos >= count($letters)) {
        // ... it returns the integer division product by the same process
        // followed by the remainder of the division
        return column_label(floor($pos / count($letters))-1) . column_label($pos % count($letters));
    } else {
        // otherwise, it just picks a index from the range
        return $letters[$pos];
    }
}