// Add term page
function summit_taxonomy_add_new_meta_field() {
	// this will add the custom meta field to the add new term page
	?>
	<div class="form-field">
    <label for="term_meta[displayed]"><?php _e( 'Display Category', 'summit' ); ?></label>
<input type="hidden" name="term_meta[helpme]" value="z">
		<input type="checkbox" name="term_meta[displayed]" id="term_meta[displayed]" value="1">
		<p class="description"><?php _e( 'Check to have the Category to displayed on the Sales Page','summit' ); ?></p>
	</div>
<?php
}
add_action( 'category_add_form_fields', 'summit_taxonomy_add_new_meta_field', 10, 2 );

// Edit term page
function summit_taxonomy_edit_meta_field($term) {

	// put the term ID into a variable
	$t_id = $term->term_id;

	// retrieve the existing value(s) for this meta field. This returns an array
	$term_meta = get_option( "taxonomy_$t_id" ); ?>
	<tr class="form-field">
    <th scope="row" valign="top"><label for="term_meta[displayed]"><?php _e( 'Display Category', 'summit' ); ?></label></th>
		<td>
<input type="hidden" name="term_meta[helpme]" value="z">
			<input type="checkbox" name="term_meta[displayed]" id="term_meta[displayed]" value="1" <?php if( isset( $term_meta['displayed'] ) ) { ?>checked="checked"<?php } ?> ">
			<p class="description"><?php _e( 'Check to have the Category to displayed on the Sales Page','summit' ); ?></p>
		</td>
	</tr>
<?php
}
add_action( 'category_edit_form_fields', 'summit_taxonomy_edit_meta_field', 10, 2 );

// Save extra taxonomy fields callback function.
function save_taxonomy_custom_meta( $term_id ) {
  $new_meta = array();
  if ( isset( $_POST['term_meta'] ) ) {
		$t_id = $term_id;
		$cat_keys = array_keys( $_POST['term_meta'] );
		foreach ( $cat_keys as $key ) {
			if ( isset ( $_POST['term_meta'][$key] ) ) {
				$new_meta[$key] = $_POST['term_meta'][$key];
			}
		}
	}
  // Save the option array.
  update_option( "taxonomy_$t_id", $new_meta );
}
add_action( 'edited_category', 'save_taxonomy_custom_meta', 10, 2 );
add_action( 'create_category', 'save_taxonomy_custom_meta', 10, 2 );