woocommerce_email_content_type │ filter-hook │ WC 1.0

Usage

add_filter( 'woocommerce_email_content_type', 'wp_kama_woocommerce_email_content_type_filter', 10, 3 );

/**
 * Function for `woocommerce_email_content_type` filter-hook.
 * 
 * @param  $content_type         
 * @param  $that                 
 * @param  $default_content_type 
 *
 * @return 
 */
function wp_kama_woocommerce_email_content_type_filter( $content_type, $that, $default_content_type ){

	// filter...
	return $content_type;
}

$content_type

-

$that

-

$default_content_type

-

Where the hook is called

return apply_filters( 'woocommerce_email_content_type', $content_type, $this, $default_content_type );

Where the hook is used in WooCommerce