print0.php

<?php
/**
 * Created by PhpStorm.
 * User: phuong
 * Date: 5/23/16
 * Time: 22:54
 */

$m = 5;
$n = 4;

$col_span = 4;
$row_span = 4;

const star = 'O';
const space = ' ';

$records = [];
$total_horizontal_chars = $n * ($row_span - 1) + 1;
$total_vertical_chars = $m * ($col_span - 1) + 1;

for ($row = 0; $row < $total_vertical_chars; $row++) {
    $record = '';
    for ($col = 0; $col < $total_horizontal_chars; $col++) {
        $thisChar = space;
        if ($row % ($row_span - 1) == 0 || $col % ($col_span - 1) == 0) {
            $thisChar = star;
        }

        $record = $record . $thisChar;
    }
    $records[] = $record;
}

$result = implode("\n", $records);

?>
<pre><?= $result; ?></pre>