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

/* form_tag handler */

add_action( 'wpcf7_init', 'wpcf7_add_form_tag_select', 10, 0 );

function wpcf7_add_form_tag_select() {
	wpcf7_add_form_tag( array( 'select', 'select*' ),
		'wpcf7_select_form_tag_handler',
		array(
			'name-attr' =&gt; true,
			'selectable-values' =&gt; true,
		)
	);
}

function wpcf7_select_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';
	}

	$atts = array();

	$atts['class'] = $tag-&gt;get_class_option( $class );
	$atts['id'] = $tag-&gt;get_id_option();
	$atts['tabindex'] = $tag-&gt;get_option( 'tabindex', 'signed_int', true );

	$atts['autocomplete'] = $tag-&gt;get_option(
		'autocomplete', '[-0-9a-zA-Z]+', true
	);

	if ( $tag-&gt;is_required() ) {
		$atts['aria-required'] = 'true';
	}

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

	$multiple = $tag-&gt;has_option( 'multiple' );
	$include_blank = $tag-&gt;has_option( 'include_blank' );
	$first_as_label = $tag-&gt;has_option( 'first_as_label' );

	if ( $tag-&gt;has_option( 'size' ) ) {
		$size = $tag-&gt;get_option( 'size', 'int', true );

		if ( $size ) {
			$atts['size'] = $size;
		} elseif ( $multiple ) {
			$atts['size'] = 4;
		} else {
			$atts['size'] = 1;
		}
	}

	if ( $data = (array) $tag-&gt;get_data_option() ) {
		$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,
	) );

	if ( $include_blank
	or empty( $values ) ) {
		array_unshift(
			$labels,
			__( '&amp;#8212;Please choose an option&amp;#8212;', 'contact-form-7' )
		);
		array_unshift( $values, '' );
	} elseif ( $first_as_label ) {
		$values[0] = '';
	}

	$html = '';
	$hangover = wpcf7_get_hangover( $tag-&gt;name );

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

		$item_atts = array(
			'value' =&gt; $value,
			'selected' =&gt; $selected,
		);

		$label = isset( $labels[$key] ) ? $labels[$key] : $value;

		$html .= sprintf(
			'&lt;option %1$s&gt;%2$s&lt;/option&gt;',
			wpcf7_format_atts( $item_atts ),
			esc_html( $label )
		);
	}

	$atts['multiple'] = (bool) $multiple;
	$atts['name'] = $tag-&gt;name . ( $multiple ? '[]' : '' );

	$html = sprintf(
		'&lt;span class=&quot;wpcf7-form-control-wrap&quot; data-name=&quot;%1$s&quot;&gt;&lt;select %2$s&gt;%3$s&lt;/select&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_select_rules',
	10, 2
);

function wpcf7_swv_add_select_rules( $schema, $contact_form ) {
	$tags = $contact_form-&gt;scan_form_tags( array(
		'type' =&gt; array( 'select*' ),
	) );

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


add_action(
	'wpcf7_swv_create_schema',
	'wpcf7_swv_add_select_enum_rules',
	20, 2
);

function wpcf7_swv_add_select_enum_rules( $schema, $contact_form ) {
	$tags = $contact_form-&gt;scan_form_tags( array(
		'basetype' =&gt; array( 'select' ),
	) );

	$values = array_reduce(
		$tags,
		function ( $values, $tag ) {
			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()
			);

			if ( $tag-&gt;has_option( 'first_as_label' ) ) {
				$tag_values = array_slice( $tag_values, 1 );
			}

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

			return $values;
		},
		array()
	);

	foreach ( $values as $field =&gt; $field_values ) {
		$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' )
				),
			) )
		);
	}
}


/* Tag generator */

add_action( 'wpcf7_admin_init', 'wpcf7_add_tag_generator_menu', 25, 0 );

function wpcf7_add_tag_generator_menu() {
	$tag_generator = WPCF7_TagGenerator::get_instance();

	$tag_generator-&gt;add( 'menu', __( 'drop-down menu', 'contact-form-7' ),
		'wpcf7_tag_generator_menu',
	 	array( 'version' =&gt; '2' )
	);
}

function wpcf7_tag_generator_menu( $contact_form, $options ) {
	$field_types = array(
		'select' =&gt; array(
			'display_name' =&gt; __( 'Drop-down menu', 'contact-form-7' ),
			'heading' =&gt; __( 'Drop-down menu form-tag generator', 'contact-form-7' ),
			'description' =&gt; __( 'Generates a form-tag for a &lt;a href=&quot;https://contactform7.com/checkboxes-radio-buttons-and-menus/&quot;&gt;drop-down menu&lt;/a&gt;.', 'contact-form-7' ),
		),
	);

	$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['select']['heading'] );
	?&gt;&lt;/h3&gt;

	&lt;p&gt;&lt;?php
		$description = wp_kses(
			$field_types['select']['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; true,
			'select_options' =&gt; array(
				'select' =&gt; $field_types['select']['display_name'],
			),
		) );

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

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

		$tgg-&gt;print( 'selectable_values', array(
			'first_as_label' =&gt; true,
		) );
	?&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>