convert column name to index number

col2idx.php

<?php

/**
 * convert column name to index number.
 * 
 * @param string $col 'Z', 'AA', 'ZAA'
 */
function col2idx($col = 'AZ') {
    $idx = 0;
    $k = count(range('A', 'Z'));
    $cols = array_reverse(str_split($cols));
    foreach ($cols as $i => $c) {
        $idx += count(range('A', $c)) * pow($k, $i);
    }
    return $idx;
}