repetir o alfabeto várias vezes como as colunas do excel

<?php

$i = 0;
$j = 0;
$columnsSize = 300;
$abc = range("A", "Z");
$abcSize = count($abc);

while ($i < $columnsSize) {

if (((int)($i / $abcSize) - $j) > 0) {

 $j++;
 echo '<br >';
 }

 echo $abc[$j - 1] . $abc[$i - ($abcSize * $j)] . ' ';

 $i++;
}

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
AA AB AC AD AE AF AG AH AI AJ AK AL AM AN AO AP AQ AR AS AT AU AV AW AX AY AZ
BA BB BC BD BE BF BG BH BI BJ BK BL BM BN BO BP BQ BR BS BT BU BV BW BX BY BZ
CA CB CC CD CE CF CG CH CI CJ CK CL CM CN CO CP CQ CR CS CT CU CV CW CX CY CZ
DA DB DC DD DE DF DG DH DI DJ DK DL DM DN DO DP DQ DR DS DT DU DV DW DX DY DZ
EA EB EC ED EE EF EG EH EI EJ EK EL EM EN EO EP EQ ER ES ET EU EV EW EX EY EZ
FA FB FC FD FE FF FG FH FI FJ FK FL FM FN FO FP FQ FR FS FT FU FV FW FX FY FZ
GA GB GC GD GE GF GG GH GI GJ GK GL GM GN GO GP GQ GR GS GT GU GV GW GX GY GZ
HA HB HC HD HE HF HG HH HI HJ HK HL HM HN HO HP HQ HR HS HT HU HV HW HX HY HZ
IA IB IC ID IE IF IG IH II IJ IK IL IM IN IO IP IQ IR IS IT IU IV IW IX IY IZ
JA JB JC JD JE JF JG JH JI JJ JK JL JM JN JO JP JQ JR JS JT JU JV JW JX JY JZ
KA KB KC KD KE KF KG KH KI KJ KK KL KM KN

Valeu William... é isso mesmo.