$i = 1;
while ($i <= 10) {
    if($i % 2) {
        echo '123<br>';
    }else {
        echo '&nbsp;&nbsp;&nbsp;&nbsp;123<br>';
    }
    $i++;
}
exit;

这样？

参考代码

$i = 0;
while (true) {
    switch ($i % 6) {
        case 0:
            echo "<p></p>";
            break;
        case 1:
            echo "<p></p>";
            break;
        case 2:
            echo "<p></p>\n";
            break;
        case 3:
            echo "    <p></p>";
            break;
        case 4:
            echo "<p></p>";
            break;
        case 5:
            echo "<p></p>\n";
            break;
        default:
            break;
    }
    $i++;
    if ($i>30) break;
}

<?php
$p    = '<p></p> ';
$pNum = 3;
$lineNum= 5;
$i      = 1;
$p    = htmlentities(str_repeat($p, $pNum) ) ;
while ( $i <= $lineNum) {
    if($i%2==0) {
        echo '&nbsp;&nbsp;'.$p.'<br />';
    } else {
        echo $p.'<br />';
    }
    ++$i;
}