Adding custom meta fields to a taxonomy.

Note that in this example name of the input is set to be an array. If the field name was not an array, then you’d have to save each field individually.

// Key of your custom taxonomy goes here.
// Taxonomy key, must not exceed 32 characters.
$prefix_taxonomy = 'category';

/**
 * This will add the custom meta field to the add new term page.
 *
 * @return void
 */
function wporg_prefix_add_meta_fields() {
	?>

	<div class="form-field term-meta-wrap">
		<label for="term_meta[custom_term_meta]">
			<?php esc_html_e( 'Example meta field', 'textdomain' ); ?>
		</label>
		<input type="text" name="term_meta[custom_term_meta]" id="term_meta[custom_term_meta]" value="" />
		<p class="description">
			<?php esc_html_e( 'Enter a value for this field.', 'textdomain' ); ?>
		</p>
	</div>
	
	<?php
}
add_action( sprintf( '%s_add_form_fields', $prefix_taxonomy ), 'wporg_prefix_add_meta_fields' );