Adding Custom Meta Box to Taxonomies

There are basically three main functions which will be used to add custom meta box for taxonomy and these functions are invoked through following hooks.

1. {taxonomy_name}_add_form_fields
2. {taxonomy_name}_edit_form_fields
3. edited_{taxonomy_name}
4. create_{taxonomy_name}

Here, we can replace taxonomy_name with any default or custom created taxonomy accordingly.I have used “Woocommerce product taxonomy” in below mentioned example code and created a plugin for same.Please check the following functions to add custom meta box:

{taxonomy_name}_add_form_fields add new custom field to add new term page form.Here I am creating a field to add a Class for term.

public function mj_taxonomy_add_custom_meta_field() {
		?>
		<div class="form-field">
			<label for="term_meta[class_term_meta]"><?php _e( 'Add Class', 'MJ' ); ?></label>
			<input type="text" name="term_meta[class_term_meta]" id="term_meta[class_term_meta]" value="">
			<p class="description"><?php _e( 'Enter a value for this field','MJ' ); ?></p>
		</div>
	<?php
	}
add_action( 'product_cat_add_form_fields', 'mj_taxonomy_add_custom_field', 10, 2 );

{taxonomy_name}_edit_form_fields add a custom field on taxonomy term edit page

public function mj_taxonomy_edit_custom_meta_field($term) {

	    $t_id = $term->term_id;
	    $term_meta = get_option( "taxonomy_$t_id" ); 
	   ?>
		<tr class="form-field">
		<th scope="row" valign="top"><label for="term_meta[class_term_meta]"><?php _e( 'Add Class', 'MJ' ); ?></label></th>
			<td>
				<input type="text" name="term_meta[class_term_meta]" id="term_meta[class_term_meta]" value="<?php echo esc_attr( $term_meta['class_term_meta'] ) ? esc_attr( $term_meta['class_term_meta'] ) : ''; ?>">
				<p class="description"><?php _e( 'Enter a value for this field','MJ' ); ?></p>
			</td>
		</tr>
	<?php
	}

add_action( 'product_cat_edit_form_fields', 'mj_taxonomy_edit_custom_meta_field', 10, 2 );

The next and last function to save to value passed through add or edit form:

public function mj_save_taxonomy_custom_meta_field( $term_id ) {
		if ( isset( $_POST['term_meta'] ) ) {
			
			$t_id = $term_id;
			$term_meta = get_option( "taxonomy_$t_id" );
			$cat_keys = array_keys( $_POST['term_meta'] );
			foreach ( $cat_keys as $key ) {
				if ( isset ( $_POST['term_meta'][$key] ) ) {
					$term_meta[$key] = $_POST['term_meta'][$key];
				}
			}
			// Save the option array.
			update_option( "taxonomy_$t_id", $term_meta );
		}
		
	}  
add_action( 'edited_product_cat', 'mj_save_taxonomy_custom_meta_field', 10, 2 );  
add_action( 'create_product_cat', 'mj_save_taxonomy_custom_meta_field', 10, 2 );