php判断复选框是否选中

<form action ="HandleFormCheckBox.php" method="post">
<ul>
  <li><input type ="checkbox" name ="category[]" value ="php">php教程</li>
  <li><input type ="checkbox" name ="category[]"  value ="java">java教程</li>
  <li><input type ="checkbox" name ="category[]" value ="mysql">mysql教程</li>
  <li><input type ="checkbox" name ="category[]" value ="html">html教程</li>
</ul>
<input type ="submit">
</form>

<?php
$checkbox_select=$_POST["category"];
print_r($checkbox_select);
?>

Array( [0]='php' [1]='java' )

<?php
$checkbox_select=$_POST["category"];
for($i=0;$i<count($checkbox_select);$i++)
{
echo "选项".$checkbox_select[$i]."被选中<br />";
}
?>