What are the similarities and differences between checkbox and radio button functionality in PHP?

Checkboxes and radio buttons are both HTML input elements used to collect user input in PHP forms. Checkboxes allow users to select multiple options, while radio buttons only allow users to select one option from a group. To implement checkbox functionality in PHP, you need to use the `$_POST` superglobal array to retrieve the selected values. For radio buttons, you can use the same method, but you need to ensure that only one radio button from the group is selected at a time.

// Checkbox functionality
if(isset($_POST['checkbox'])){
    foreach($_POST['checkbox'] as $selected){
        echo $selected."<br>";
    }
}

// Radio button functionality
if(isset($_POST['radio'])){
    $selected = $_POST['radio'];
    echo $selected;
}