Handling radio and checkbox in a form with PHP

This article introduces how to handle radio and checkbox in a form with PHP and gives a live demo to demonstrate it.

HTML form

In a HTML form, you need to specify the name and value attributes in radio and checkbox elements. Specially the names for checkbox group need to end with [], then the submitted checkbox data will be an array in the form handler. For a single checkbox, its name does not need to be end with [], its handling is similar to the radio.

A form with radio and checkbox

HTML code

<form action="action.php" method="post">
<div>
  <label for="name">Name:</label>
  <input id="name" type="text" name="name" >
</div>    
<div>
  <input type="radio" name="gender" id="female" value="Female">
  <label for="female">Female</label>
  <input type="radio" name="gender" id="male" value="Male">
  <label for="male">Male</label>
</div>
<div>
  <input type="checkbox" name="sports[]" id="badminton" value="Badminton">
  <label for="badmiton">Badminton</label>
  <input type="checkbox" name="sports[]" id="tennis"  value="Tennis">
  <label for="tennis">Tennis</label>  
  <input type="checkbox" name="sports[]" id="table-tennis" value="Table Tennis">
  <label for="table-tennis">Table Tennis</label>
  <input type="checkbox" name="sports[]" id="swimming" value="Swimming">
  <label for="swimming">Swimming</label>
  <input type="checkbox" name="sports[]" id="other" value="Other">
  <label for="other">Other</label>
</div>    
</form>

Effect

PHP handling

In the PHP handler of the form above, if a radio is checked, the $_POST['gender'] will be its value. If no radio is checked, $_POST['gender'] will be unset (meaning isset( $_POST['gender'] ) is false). If one or more checkboxes are checked, $_POST['sports'] will be an array containing all the checked values, otherwise it will be unset.

PHP form handling code in the action.php file:

<?php
    if ( isset( $_POST['name'] ) ) {
        echo '<p>Your name is ' . $_POST['name'] . '</p>';
    } else {
        echo '<p>Your name is unset.</p>';
    }

    // radio
    if ( isset( $_POST['gender'] ) ) {
        echo '<p>You are ' . $_POST['gender'] . '</p>';
    } else {
        echo '<p>Your gender is unset</p>';
    }

    // checkbox
    // If the user did not select any sport, $_POST['sports'] will be unset.
    if( empty( $_POST['sports'] ) ) { 
        echo 'You did not select any favorite sports.';
    } else { // Return an array containing checked strings.
        echo '<p>Your favorite sports:</br>';
        foreach ( $_POST['sports'] as $s ) {
            echo '- ' . $s . '</br>';
        }
        echo '</p>';                            
    }      
?>

See a live demo: Handling radio and checkbox in a form with PHP demo.