wp-checkbox-settings-field.php

<?php
/** 
 * Parse HTML for 'checkbox' field
 * @input type checkbox
 */
function unitizr_removestyles_field_cb($args)
{ 
    $checked = '';
    $options = get_option($args['option_name']);
    $value   = ( !isset( $options[$args['name']] ) ) 
                ? null : $options[$args['name']];
    if($value) { $checked = ' checked="checked" '; }

        $html = '';
        $html .= '<input id="' . $args['name'] . '" 
        name="' . esc_attr( $args['option_name'] . '['.$args['name'].']') .'" 
        type="checkbox" ' . $checked . '/>';
        $html .= '<span class="wndspan">' . $args['description'] .'</span>';
        $html .= '<b class="wntip" data-title="'. $args['tip'] .'"> ? </b>';
        echo $html;
}    

/* The settings arguments */
// c9.) settings checkbox 
    add_settings_field(
        'unitizr_removestyles_field',
        esc_attr__('Remove Unitizr Styles', 'unitizr'),
        'unitizr_removestyles_field_cb',
        'unitizr_options',
        'unitizr_options_section',
        array( 
            'type'        => 'checkbox',
            'option_name' => 'unitizr_options', 
            'name'        => 'unitizr_removestyles_field',
            'label_for'   => 'unitizr_removestyles_field',
            'value'       => (empty(get_option('unitizr_options')['unitizr_removestyles_field']))
                              ? 0 : get_option('unitizr_options')['unitizr_removestyles_field'],
            'description' => esc_html__( 'Check to remove Unitizr premade Woocommerce overrides.', 'unitizr' ),
            'checked'     => (!isset(get_option('unitizr_options')['unitizr_removestyles_field']))
                               ? 0 : get_option('unitizr_options')['unitizr_removestyles_field'],
           
            'tip'         => esc_attr__( 'Use if Woocommerce fields drastically changed when installing this plugin.', 'unitizr' ) 
            )
    );