如果没有选中单选按钮，如何提交表单

Question

I using PHP in order to create an HTML form.
The form has 3 radio buttons and a submit button.
In the initial state of the form, none of the radio buttons is checked.
I want to make the form not to be submitted if non of the radio buttons is checked.
Is there any way to do that? I attached part of the PHP code.

    for($i=0; $i<$nChoices; $i++) {
$Text='<input type="radio" name="answer" value="' . $IdChoices[$i] . '"';
$Text.=">  ". $Choices[$i] . "</input>";
$choiceoutput.= $Text."<br /><br />";
}

Thanks!

Answer 1

This javascript can be used for simple client-side validation. It's not considered safe to only validate on the client-side but if your purpose is to see if the user actually selected an value this will do. Otherwise further validation needs to be taking place in your php script.

<script type="text/javascript">
function validate()
{
  var retval = false;
  for (var i=0; i < document.myForm.r.length; i++)
  {
    if (document.myForm.r[i].checked)
    {
      retval = true;
    }
  }  

  return retval;
}
</script>

Simple form for putting it to work.

<form name="myForm" action="page.php" onsubmit="return validate()" method="post">
<input type="radio" id="r">
<input type="radio" id="r">
<input type="submit" value="ok">
</form>