<?php for ( $i = 1; $i <= 10; ++$i ) echo ( ( $i - 1 ) % 4 ? '' : '<div class="row">' . "\n" ) . "\t<span>$i</span>\n" . ( $i - 10 && $i % 4 ? '' : "</div>\n" ); ?>
Standard input is empty
<div class="row"> <span>1</span> <span>2</span> <span>3</span> <span>4</span> </div> <div class="row"> <span>5</span> <span>6</span> <span>7</span> <span>8</span> </div> <div class="row"> <span>9</span> <span>10</span> </div>