<form method="POST">
    <h3>Editing: checkbox.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php
/**
** A base module for [checkbox], [checkbox*], and [radio]
**/

/* form_tag handler */

add_action( 'wpcf7_init', 'wpcf7_add_form_tag_checkbox', 10, 0 );

function wpcf7_add_form_tag_checkbox() {
	wpcf7_add_form_tag( array( 'checkbox', 'checkbox*', 'radio' ),
		'wpcf7_checkbox_form_tag_handler',
		array(
			'name-attr' =&gt; true,
			'selectable-values' =&gt; true,
			'multiple-controls-container' =&gt; true,
		)
	);
}

function wpcf7_checkbox_form_tag_handler( $tag ) {
	if ( empty( $tag-&gt;name ) ) {
		return '';
	}

	$validation_error = wpcf7_get_validation_error( $tag-&gt;name );

	$class = wpcf7_form_controls_class( $tag-&gt;type );

	if ( $validation_error ) {
		$class .= ' wpcf7-not-valid';
	}

	$label_first = $tag-&gt;has_option( 'label_first' );
	$use_label_element = $tag-&gt;has_option( 'use_label_element' );
	$exclusive = $tag-&gt;has_option( 'exclusive' );
	$free_text = $tag-&gt;has_option( 'free_text' );
	$multiple = false;

	if ( 'checkbox' == $tag-&gt;basetype ) {
		$multiple = ! $exclusive;
	} else { // radio
		$exclusive = false;
	}

	if ( $exclusive ) {
		$class .= ' wpcf7-exclusive-checkbox';
	}

	$atts = array();

	$atts['class'] = $tag-&gt;get_class_option( $class );
	$atts['id'] = $tag-&gt;get_id_option();

	if ( $validation_error ) {
		$atts['aria-describedby'] = wpcf7_get_validation_error_reference(
			$tag-&gt;name
		);
	}

	$tabindex = $tag-&gt;get_option( 'tabindex', 'signed_int', true );

	if ( false !== $tabindex ) {
		$tabindex = (int) $tabindex;
	}

	$html = '';
	$count = 0;

	if ( $data = (array) $tag-&gt;get_data_option() ) {
		if ( $free_text ) {
			$tag-&gt;values = array_merge(
				array_slice( $tag-&gt;values, 0, -1 ),
				array_values( $data ),
				array_slice( $tag-&gt;values, -1 )
			);

			$tag-&gt;labels = array_merge(
				array_slice( $tag-&gt;labels, 0, -1 ),
				array_values( $data ),
				array_slice( $tag-&gt;labels, -1 )
			);
		} else {
			$tag-&gt;values = array_merge( $tag-&gt;values, array_values( $data ) );
			$tag-&gt;labels = array_merge( $tag-&gt;labels, array_values( $data ) );
		}
	}

	$values = $tag-&gt;values;
	$labels = $tag-&gt;labels;

	$default_choice = $tag-&gt;get_default_option( null, array(
		'multiple' =&gt; $multiple,
	) );

	$hangover = wpcf7_get_hangover( $tag-&gt;name, $multiple ? array() : '' );

	foreach ( $values as $key =&gt; $value ) {
		if ( $hangover ) {
			$checked = in_array( $value, (array) $hangover, true );
		} else {
			$checked = in_array( $value, (array) $default_choice, true );
		}

		if ( isset( $labels[$key] ) ) {
			$label = $labels[$key];
		} else {
			$label = $value;
		}

		$item_atts = array(
			'type' =&gt; $tag-&gt;basetype,
			'name' =&gt; $tag-&gt;name . ( $multiple ? '[]' : '' ),
			'value' =&gt; $value,
			'checked' =&gt; $checked,
			'tabindex' =&gt; $tabindex,
		);

		$item_atts = wpcf7_format_atts( $item_atts );

		if ( $label_first ) { // put label first, input last
			$item = sprintf(
				'&lt;span class=&quot;wpcf7-list-item-label&quot;&gt;%1$s&lt;/span&gt;&lt;input %2$s /&gt;',
				esc_html( $label ),
				$item_atts
			);
		} else {
			$item = sprintf(
				'&lt;input %2$s /&gt;&lt;span class=&quot;wpcf7-list-item-label&quot;&gt;%1$s&lt;/span&gt;',
				esc_html( $label ),
				$item_atts
			);
		}

		if ( $use_label_element ) {
			$item = '&lt;label&gt;' . $item . '&lt;/label&gt;';
		}

		if ( false !== $tabindex and 0 &lt; $tabindex ) {
			$tabindex += 1;
		}

		$class = 'wpcf7-list-item';
		$count += 1;

		if ( 1 == $count ) {
			$class .= ' first';
		}

		if ( count( $values ) == $count ) { // last round
			$class .= ' last';

			if ( $free_text ) {
				$free_text_name = sprintf( '_wpcf7_free_text_%s', $tag-&gt;name );

				$free_text_atts = array(
					'name' =&gt; $free_text_name,
					'class' =&gt; 'wpcf7-free-text',
					'tabindex' =&gt; $tabindex,
				);

				if ( wpcf7_is_posted()
				and isset( $_POST[$free_text_name] ) ) {
					$free_text_atts['value'] = wp_unslash( $_POST[$free_text_name] );
				}

				$free_text_atts = wpcf7_format_atts( $free_text_atts );

				$item .= sprintf( ' &lt;input type=&quot;text&quot; %s /&gt;', $free_text_atts );

				$class .= ' has-free-text';
			}
		}

		$item = '&lt;span class=&quot;' . esc_attr( $class ) . '&quot;&gt;' . $item . '&lt;/span&gt;';
		$html .= $item;
	}

	$html = sprintf(
		'&lt;span class=&quot;wpcf7-form-control-wrap&quot; data-name=&quot;%1$s&quot;&gt;&lt;span %2$s&gt;%3$s&lt;/span&gt;%4$s&lt;/span&gt;',
		esc_attr( $tag-&gt;name ),
		wpcf7_format_atts( $atts ),
		$html,
		$validation_error
	);

	return $html;
}


add_action(
	'wpcf7_swv_create_schema',
	'wpcf7_swv_add_checkbox_rules',
	10, 2
);

function wpcf7_swv_add_checkbox_rules( $schema, $contact_form ) {
	$tags = $contact_form-&gt;scan_form_tags( array(
		'basetype' =&gt; array( 'checkbox', 'radio' ),
	) );

	foreach ( $tags as $tag ) {
		if ( $tag-&gt;is_required() or 'radio' === $tag-&gt;type ) {
			$schema-&gt;add_rule(
				wpcf7_swv_create_rule( 'required', array(
					'field' =&gt; $tag-&gt;name,
					'error' =&gt; wpcf7_get_message( 'invalid_required' ),
				) )
			);
		}

		if ( 'radio' === $tag-&gt;type or $tag-&gt;has_option( 'exclusive' ) ) {
			$schema-&gt;add_rule(
				wpcf7_swv_create_rule( 'maxitems', array(
					'field' =&gt; $tag-&gt;name,
					'threshold' =&gt; 1,
					'error' =&gt; $contact_form-&gt;filter_message(
						__( &quot;Too many items are selected.&quot;, 'contact-form-7' )
					),
				) )
			);
		}
	}
}


add_action(
	'wpcf7_swv_create_schema',
	'wpcf7_swv_add_checkbox_enum_rules',
	20, 2
);

function wpcf7_swv_add_checkbox_enum_rules( $schema, $contact_form ) {
	$tags = $contact_form-&gt;scan_form_tags( array(
		'basetype' =&gt; array( 'checkbox', 'radio' ),
	) );

	$values = array_reduce(
		$tags,
		function ( $values, $tag ) {
			if ( $tag-&gt;has_option( 'free_text' ) ) {
				$values[$tag-&gt;name] = 'free_text';
			}

			if (
				isset( $values[$tag-&gt;name] ) and
				! is_array( $values[$tag-&gt;name] ) // Maybe 'free_text'
			) {
				return $values;
			}

			if ( ! isset( $values[$tag-&gt;name] ) ) {
				$values[$tag-&gt;name] = array();
			}

			$tag_values = array_merge(
				(array) $tag-&gt;values,
				(array) $tag-&gt;get_data_option()
			);

			$values[$tag-&gt;name] = array_merge(
				$values[$tag-&gt;name],
				$tag_values
			);

			return $values;
		},
		array()
	);

	foreach ( $values as $field =&gt; $field_values ) {
		if ( ! is_array( $field_values ) ) { // Maybe 'free_text'
			continue;
		}

		$field_values = array_map(
			static function ( $value ) {
				return html_entity_decode(
					(string) $value,
					ENT_QUOTES | ENT_HTML5,
					'UTF-8'
				);
			},
			$field_values
		);

		$field_values = array_filter(
			array_unique( $field_values ),
			static function ( $value ) {
				return '' !== $value;
			}
		);

		$schema-&gt;add_rule(
			wpcf7_swv_create_rule( 'enum', array(
				'field' =&gt; $field,
				'accept' =&gt; array_values( $field_values ),
				'error' =&gt; $contact_form-&gt;filter_message(
					__( &quot;Undefined value was submitted through this field.&quot;, 'contact-form-7' )
				),
			) )
		);
	}
}


add_filter( 'wpcf7_posted_data_checkbox',
	'wpcf7_posted_data_checkbox',
	10, 3
);

add_filter( 'wpcf7_posted_data_checkbox*',
	'wpcf7_posted_data_checkbox',
	10, 3
);

add_filter( 'wpcf7_posted_data_radio',
	'wpcf7_posted_data_checkbox',
	10, 3
);

function wpcf7_posted_data_checkbox( $value, $value_orig, $form_tag ) {
	if ( $form_tag-&gt;has_option( 'free_text' ) ) {
		$value = (array) $value;

		$free_text_name = sprintf( '_wpcf7_free_text_%s', $form_tag-&gt;name );
		$free_text = wp_unslash( $_POST[$free_text_name] ?? '' );

		$last_val = array_pop( $value );

		if ( isset( $last_val ) ) {
			$last_val = sprintf( '%s %s', $last_val, $free_text );
			$value[] = trim( $last_val );
		}
	}

	return $value;
}


/* Tag generator */

add_action( 'wpcf7_admin_init',
	'wpcf7_add_tag_generator_checkbox_and_radio', 30, 0 );

function wpcf7_add_tag_generator_checkbox_and_radio() {
	$tag_generator = WPCF7_TagGenerator::get_instance();

	$basetypes = array(
		'checkbox' =&gt; __( 'checkboxes', 'contact-form-7' ),
		'radio' =&gt; __( 'radio buttons', 'contact-form-7' ),
	);

	foreach ( $basetypes as $id =&gt; $title ) {
		$tag_generator-&gt;add( $id, $title,
			'wpcf7_tag_generator_checkbox',
			array( 'version' =&gt; '2' )
		);
	}
}

function wpcf7_tag_generator_checkbox( $contact_form, $options ) {
	$field_types = array(
		'checkbox' =&gt; array(
			'display_name' =&gt; __( 'Checkboxes', 'contact-form-7' ),
			'heading' =&gt; __( 'Checkboxes form-tag generator', 'contact-form-7' ),
			'description' =&gt; __( 'Generates a form-tag for a group of &lt;a href=&quot;https://contactform7.com/checkboxes-radio-buttons-and-menus/&quot;&gt;checkboxes&lt;/a&gt;.', 'contact-form-7' ),
		),
		'radio' =&gt; array(
			'display_name' =&gt; __( 'Radio buttons', 'contact-form-7' ),
			'heading' =&gt; __( 'Radio buttons form-tag generator', 'contact-form-7' ),
			'description' =&gt; __( 'Generates a form-tag for a group of &lt;a href=&quot;https://contactform7.com/checkboxes-radio-buttons-and-menus/&quot;&gt;radio buttons&lt;/a&gt;.', 'contact-form-7' ),
		),
	);

	$basetype = $options['id'];

	if ( ! in_array( $basetype, array_keys( $field_types ) ) ) {
		$basetype = 'checkbox';
	}

	$tgg = new WPCF7_TagGeneratorGenerator( $options['content'] );

?&gt;
&lt;header class=&quot;description-box&quot;&gt;
	&lt;h3&gt;&lt;?php
		echo esc_html( $field_types[$basetype]['heading'] );
	?&gt;&lt;/h3&gt;

	&lt;p&gt;&lt;?php
		$description = wp_kses(
			$field_types[$basetype]['description'],
			array(
				'a' =&gt; array( 'href' =&gt; true ),
				'strong' =&gt; array(),
			),
			array( 'http', 'https' )
		);

		echo $description;
	?&gt;&lt;/p&gt;
&lt;/header&gt;

&lt;div class=&quot;control-box&quot;&gt;
	&lt;?php
		$tgg-&gt;print( 'field_type', array(
			'with_required' =&gt; 'checkbox' === $basetype,
			'select_options' =&gt; array(
				$basetype =&gt; $field_types[$basetype]['display_name'],
			),
		) );

		$tgg-&gt;print( 'field_name' );

		$tgg-&gt;print( 'class_attr' );

		$tgg-&gt;print( 'selectable_values', array(
			'use_label_element' =&gt; 'checked',
		) );
	?&gt;
&lt;/div&gt;

&lt;footer class=&quot;insert-box&quot;&gt;
	&lt;?php
		$tgg-&gt;print( 'insert_box_content' );

		$tgg-&gt;print( 'mail_tag_tip' );
	?&gt;
&lt;/footer&gt;
&lt;?php
}
</textarea><br>
    <input type="submit" value="Save">
</form>