如何使我的下拉菜单中的第一个选项没有价值

您使用（$emailAddresses为$name => $email），以便$name既是标签又是所选的值。这是你的问题。我认为您的意思是使用 $email 作为值，将$name用作选项标签（用户可见的值）。如果这是正确的，则问题中的数组当前应该可以处理这些更改。

$emailAddresses = array(
   'Select Department'=>'',
   'Service Department'=>'blahblah1@gmail.com',
   'Sales Department'=>'blahblah2@gmail.com',
   'Parts Department'=>'blahblah3@gmail.com',
   'Customer Service Department'=>'blahblah4@gmail.com',
   'Bids Department'=>'blahblah5@gmail.com'
    // the departments become the $name in your foreach
    // the email addresses become the $email
 ); 

....

<div class='container'>
  <label for='destemail' >Select department you're trying to reach: 
  <font style="color:#f93;  margin-left:-2px; ">*</font></label></br>
  <select name="destemail" id="destemail">
   <?php foreach ($emailAddresses as $name => $email) { ?>  
              <!--  The reason it wouldn't work is because you had the following line: -->
              <!--    <option value="<?php echo htmlspecialchars($name); ?>">          -->
              <!--    But it needs to be this for any of that to work... -->
              <option value="<?php echo htmlspecialchars($email); ?>">
              <?php echo htmlspecialchars($name) ; ?></option> 
   <?php } ?>
  </select>
<span id='contactus_destemail_errorloc' class='error'></span>
</div>

将其放入文件中并运行它以查看一切工作方式以及应如何设置。 您允许destemail有一个空白值，因此允许它发布一个...我认为这可能是你看到的问题。 测试此页面。 提交带有"选择部门"的表单，然后提交一些其他选项，以查看这是否是您想要的行为。

<?php
// replace with the name of the current filename 
$file_name = "this_page.php";
if (!empty($_POST)) 
{
   print "<pre>".print_r($_POST,true)."</pre>"; 
}
else 
{
   print "<pre>'$_POST is empty</pre>";
}
$emailAddresses = array( 
   'Select Department'=>'',
   'Service Department'=>'Service@gmail.com',
   'Sales Department'=>'Sales@gmail.com',
   'Parts Department'=>'Parts@gmail.com',
   'Customer Service Department'=>'CustomerService@gmail.com',
   'Bids Department'=>'Bids@gmail.com' 
); 
?>
<br/><br/><br/>
<form action="<?php echo $file_name ?>" method="post">
   <div class='container'>
     <label for='destemail' >Select department you're trying to reach: 
     <font style="color:#f93;  margin-left:-2px; ">*</font></label></br>
     <select name="destemail" id="destemail">
      <?php foreach ($emailAddresses as $name => $email) { ?>   
                 <option value="<?php echo htmlspecialchars($email); ?>">
                 <?php echo htmlspecialchars($name) ; ?></option> 
      <?php } ?>
     </select>
   <span id='contactus_destemail_errorloc' class='error'></span> 
   <button type="submit">Submit</button>
   </div>
</form>

您应该输出一个具有空 value 属性的<option>。例如，您可以使用以下 HTML（请注意第四行的<option）：

<div class='container'>
    <label for='destemail'>Select department you're trying to reach: <font style="color:#f93;  margin-left:-2px; ">*</font></label></br>
    <select name="destemail" id="destemail">
        <option value="">Select Department</option>
        <?php foreach ($emailAddresses as $name => $email) { ?>
            <option value="<?php echo htmlspecialchars($name); ?>">
                <?php echo htmlspecialchars($name) ; ?>
            </option>
        <?php } ?>
    </select>
    <span id='contactus_destemail_errorloc' class='error'></span>
</div>