phtml文件列表中的强制检查字段

i have a list which contains some element.How can i put mandatory check in this list since select required is not supported by any major browser.

<th>From *</th>
<th><select name="from">
        <option value="builder">Builder</option>
        <option value="broker">Broker</option>
        <option value="seeker">Seeker</option>
        <option value="owner">Owner</option>
        <option value="regular cf user">Regular CF user</option>
        <option value="ams user">AMS user</option>
        <option value="home needs user">Home Needs User</option>
</select>
</th>

this is my given list i want to check for mandatory field.

Once you POST the form, just check for the value, and if it is empty/missing, show an error:

if (! isset($_POST['from']) || empty($_POST['from']))
{
    // Deal with the fact that a mandatory field was not provided.
} 

Use javascript.

<th>From *</th>
<th><select name="from" onchange="return validate();">
        <option value="">Select One</option>
        <option value="builder">Builder</option>
        <option value="broker">Broker</option>
        <option value="seeker">Seeker</option>
        <option value="owner">Owner</option>
        <option value="regular cf user">Regular CF user</option>
        <option value="ams user">AMS user</option>
        <option value="home needs user">Home Needs User</option>
</select>
</th>

Javascript

  <script type="text/javascript>
    function validate()
    {
        var from=document.getElementsByName('from').value;
        if(from==""){
           alert('Please select an option');
       }
       return true;
    }
   </script>: