PHP自我验证表单复选框

Question

我有一个PHP自我验证表单，它验证所有字段但不报告要输出的复选框。我似乎无法找到一个澄清的例子。请帮忙！

 //make sure one of the services requested checkboxes are checked
$require_one_of = array('walkSale','RawSale','groomSale'); //names of posted checkboxes
$one_set=false;
foreach($require_one_of as $key){
 if(isset($_POST[$key])){
  $one_set=true;
  break;
}
}
if(!$one_set){
//error handling
 $reasonErr= "You forgot to select a Service!";
}

HTML表单

 <fieldset id="field3">
  <legend id="legend3">Services Required:</legend>
  <hr />
  <input type="checkbox" name="walkSale" value="walkSale"
  <?php if(isset($_POST['walkSale'])) echo "checked='checked'";?> class="textfield"/>I'm looking for a Dog Walker!&nbsp;

  <input type="checkbox" name="RawSale" value="RawSale"
  <?php if(isset($_POST['RawSale'])) echo "checked='checked'";?> class="textfield"/>I'm looking to purchase Raw Food!&nbsp;

  <input type="checkbox" name="groomSale" value="groomSale"
  <?php if(isset($_POST['groomSale'])) echo "checked='checked'";?> class="textfield"/>I'm looking for a Dog Groomer!

  <span class="error">* <?php echo $reasonErr;?></span>

</fieldset>