which is plugin base directory wordpress code example

Example 1: how to get plugin directory path in wordpress

if ( is_admin() ) {
    include_once( plugin_dir_path( __FILE__ ) . 'includes/admin-functions.php' );
} else {
    include_once( plugin_dir_path( __FILE__ ) . 'includes/front-end-functions.php' );
}

Example 2: how to get plugin directory path in wordpress

function plugin_dir_path( $file ) {
    return trailingslashit( dirname( $file ) );
}