What are common debugging techniques for PHP scripts when encountering issues like data not being updated in checkboxes?

When encountering issues with data not being updated in checkboxes in PHP scripts, it is important to check the value of the checkbox input in the form submission. Ensure that the checkbox input has the correct name attribute and that it is being properly processed in the PHP script handling the form submission. Additionally, check if the checkbox input is being correctly set to "checked" based on the data being retrieved from the database or form submission.

// HTML form with checkbox input
<form method="post">
    <input type="checkbox" name="checkbox_name" value="1" <?php if($checkbox_value == 1) echo "checked"; ?>>
    <input type="submit" name="submit" value="Submit">
</form>

// PHP script handling form submission
if(isset($_POST['submit'])) {
    $checkbox_value = isset($_POST['checkbox_name']) ? 1 : 0;
    
    // Update database with $checkbox_value
}