一个表单中的两个select标记，POST方法仅获取一个select标记的值

<form action="process_form.php" method="post">
  <label for="select1">Select 1:</label>
  <select id="select1" name="select1">
    <option value="option1">Option 1</option>
    <option value="option2">Option 2</option>
    <option value="option3">Option 3</option>
  </select>
  
  <label for="select2">Select 2:</label>
  <select id="select2" name="select2">
    <option value="option4">Option 4</option>
    <option value="option5">Option 5</option>
    <option value="option6">Option 6</option>
  </select>
  
  <input type="submit" value="Submit">
</form>

<?php
$select1_value = $_POST['select1'];
// 只获取select1标记的值

// 进行后续处理...
?>