which radio button is checked?

Question

I wanted to check which radio button is checked. Then, I looked at the questions in here before i asked this question and they said that the code

        if(document.getElementById('number1').checked) 

is the answer. But, i got the error "Use of undefined constant document - assumed 'document'" and

Call to undefined function getElementById().

Where did it go wrong? Did i have to write the function of getElementById('number1').checked because it says "undefined"? Thanks

Answer 1

Your code is Javascript. To check the value of a radio button in PHP, it needs to have a name attribute, which was sent in a form either by a GET or POST.

// If form method='get'
if (isset($_GET['name_of_radio_group'])) {

  // Show the radio button value, i.e. which one was checked when the form was sent
  echo $_GET['name_of_radio_group'];
}

// If form method='post'
if (isset($_POST['name_of_radio_group'])) {

  // Show the radio button value, i.e. which one was checked when the form was sent
  echo $_POST['name_of_radio_group'];
}

Answer 2

The code you have posted is in JavaScript. In order to determine is to submit a form as a post or get and query the value with the superglobals $_POST[], $_GET[], $_REQUEST[].

You have your HTML code:

<input type="radio" name="radio_group1" value="rg1v1" />Radio Group 1 - Value 1<br />
<input type="radio" name="radio_group1" value="rg1v2" />Radio Group 1 - Value 2<br />
<input type="radio" name="radio_group1" value="rg1v3" />Radio Group 1 - Value 3<br />

Assuming that you submitted the form using the post method to your php file the following code will test for which radio button is selected.

<?php
    switch($_POST['radio_group1']) {
        case "rg1v1":
            $value = "Radio Group 1 - Value 1 has been selected.";
            break;
        case "rg1v2":
            $value = "Radio Group 1 - Value 2 has been selected.";
            break;
        case "rg1v3":
            $value = "Radio Group 1 - Value 3 has been selected.";
            break;
        default:
            $value = "No radio has been selected for Radio Group 1";
    }
?>