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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>First Steps Into PHP</title>
    <style>
        table * {
            border: 1px solid black;
            width: 50px;
            height: 50px;
        }
    </style>
</head>
<body>
<table>
    <tr>
        <td>
            Red
        </td>
        <td>
            Green
        </td>
        <td>
            Blue
        </td>
    </tr>
    <?php
    for($i=51;$i<=255;$i+=51){
    ?>
    <tr>
        <td style="background: RGB(<?=$i?>, 0, 0)"></td>
        <td style="background: RGB(0, <?=$i?>, 0)"></td>
        <td style="background: RGB(0, 0, <?=$i?>)"></td>
    </tr>
<?php}?>
</table>
</body>
</html>