PHP中余数、取余的妙用

<?php
 
$ary=array("name","egineer","sonny","tonny","pingk","apple","phone","clone","pink","colle");
foreach($ary as $key=>$value){
$key=$key+1;
if($key%2==1){echo '<li>';}
  ?>
 <span><?php echo $key.":". $value;?></span>
 
<?php
 if($key%2==0){echo '</li>';}
};
 ?>

 <?php
 
$ary=array("name","egineer","sonny","tonny","pingk","apple","phone","clone","pink","colle");
foreach($ary as $key=>$value){
$key=$key;
if($key%3==0){echo '<li>';}
  ?>
 <span class="<?php echo($key%3); ?>span"><?php echo $key.":". $value;?></span>
 
<?php
 if($key%3==2){echo '</li>';}
};
 ?>