Term Meta Generator

<?php
/**
 * Extra fields on category terms.
 */

/**
 * Registers the meta keys.
 *
 * This is what types the value and checks permission wherever it is written
 * from, not only through the forms below.
 */
function my_plugin_register_term_meta() {
	register_term_meta(
		'category',
		'my_plugin_subtitle',
		array(
			'type'              => 'string',
			'single'            => true,
			'show_in_rest'      => false,
			'sanitize_callback' => 'sanitize_text_field',
			'auth_callback'     => 'my_plugin_can_edit_term_meta',
		)
	);
	register_term_meta(
		'category',
		'my_plugin_featured',
		array(
			'type'              => 'string',
			'single'            => true,
			'show_in_rest'      => false,
			'sanitize_callback' => 'sanitize_text_field',
			'auth_callback'     => 'my_plugin_can_edit_term_meta',
		)
	);
}
add_action( 'init', 'my_plugin_register_term_meta' );

/**
 * Decides who may write these keys outside the forms.
 *
 * @param bool   $allowed Current decision.
 * @param string $key     Meta key.
 * @param int    $term_id Term ID.
 * @return bool
 */
function my_plugin_can_edit_term_meta( $allowed, $key, $term_id ) {
	return current_user_can( 'manage_categories' );
}

/**
 * The fields on the Add Term form.
 *
 * This form has no term yet, so there is nothing to read: only defaults.
 */
function my_plugin_term_add_fields() {
	wp_nonce_field( 'my_plugin_term_meta', 'my_plugin_nonce' );

	echo '<div class="form-field">';
	printf(
		'<label for="%1$s">%2$s</label><input type="text" id="%1$s" name="%1$s" value="" />',
		esc_attr( 'my_plugin_subtitle' ),
		esc_html__( 'Subtitle', 'my-plugin' )
	);
	echo '<p>' . esc_html__( 'Shown under the term name on the archive.', 'my-plugin' ) . '</p>';
	echo '</div>';

	echo '<div class="form-field">';
	printf(
		'<label for="%1$s"><input type="checkbox" id="%1$s" name="%1$s" value="1" /> %2$s</label>',
		esc_attr( 'my_plugin_featured' ),
		esc_html__( 'Feature this term', 'my-plugin' )
	);
	echo '</div>';
}
add_action( 'category_add_form_fields', 'my_plugin_term_add_fields' );

/**
 * The fields on the Edit Term form.
 *
 * A different markup shape from the add form: this one is a table.
 *
 * @param WP_Term $term The term being edited.
 */
function my_plugin_term_edit_fields( $term ) {
	wp_nonce_field( 'my_plugin_term_meta', 'my_plugin_nonce' );

	$value = get_term_meta( $term->term_id, 'my_plugin_subtitle', true );

	echo '<tr class="form-field">';
	printf(
		'<th scope="row"><label for="%1$s">%2$s</label></th>',
		esc_attr( 'my_plugin_subtitle' ),
		esc_html__( 'Subtitle', 'my-plugin' )
	);
	echo '<td>';
	printf(
		'<input type="text" id="%1$s" name="%1$s" value="%2$s" class="regular-text" />',
		esc_attr( 'my_plugin_subtitle' ),
		esc_attr( $value )
	);
	echo '<p class="description">' . esc_html__( 'Shown under the term name on the archive.', 'my-plugin' ) . '</p>';
	echo '</td></tr>';

	$value = get_term_meta( $term->term_id, 'my_plugin_featured', true );

	echo '<tr class="form-field">';
	printf(
		'<th scope="row"><label for="%1$s">%2$s</label></th>',
		esc_attr( 'my_plugin_featured' ),
		esc_html__( 'Feature this term', 'my-plugin' )
	);
	echo '<td>';
	printf(
		'<input type="checkbox" id="%1$s" name="%1$s" value="1"%2$s />',
		esc_attr( 'my_plugin_featured' ),
		checked( $value, '1', false )
	);
	echo '</td></tr>';
}
add_action( 'category_edit_form_fields', 'my_plugin_term_edit_fields' );

/**
 * Saves the fields.
 *
 * Both hooks call this: created_ for a new term, edited_ for an existing one.
 *
 * @param int $term_id The term.
 */
function my_plugin_save_term_meta( $term_id ) {
	if ( ! isset( $_POST['my_plugin_nonce'] ) ) {
		return;
	}

	$nonce = sanitize_text_field( wp_unslash( $_POST['my_plugin_nonce'] ) );

	if ( ! wp_verify_nonce( $nonce, 'my_plugin_term_meta' ) ) {
		return;
	}

	if ( ! current_user_can( 'manage_categories' ) ) {
		return;
	}

	if ( empty( $_POST['my_plugin_subtitle'] ) ) {
		delete_term_meta( $term_id, 'my_plugin_subtitle' );
	} else {
		update_term_meta(
			$term_id,
			'my_plugin_subtitle',
			sanitize_text_field( wp_unslash( $_POST['my_plugin_subtitle'] ) )
		);
	}

	if ( empty( $_POST['my_plugin_featured'] ) ) {
		delete_term_meta( $term_id, 'my_plugin_featured' );
	} else {
		update_term_meta( $term_id, 'my_plugin_featured', '1' );
	}
}
add_action( 'created_category', 'my_plugin_save_term_meta' );
add_action( 'edited_category', 'my_plugin_save_term_meta' );

/**
 * Adds a column for subtitle to the terms list.
 *
 * @param array $columns Existing columns.
 * @return array
 */
function my_plugin_term_columns( $columns ) {
	$columns['my_plugin_subtitle'] = esc_html__( 'Subtitle', 'my-plugin' );

	return $columns;
}
add_filter( 'manage_edit-category_columns', 'my_plugin_term_columns' );

/**
 * Fills the column.
 *
 * @param string $content Current content.
 * @param string $column  Column name.
 * @param int    $term_id The term.
 * @return string
 */
function my_plugin_term_column_content( $content, $column, $term_id ) {
	if ( 'my_plugin_subtitle' !== $column ) {
		return $content;
	}

	return esc_html( (string) get_term_meta( $term_id, 'my_plugin_subtitle', true ) );
}
add_filter( 'manage_category_custom_column', 'my_plugin_term_column_content', 10, 3 );