WP-CLI with theme: Uncaught Error: Class ‘WP_CLI’ not found
You’ll need to wrap your statement within a class_exists() check: function foo_command( $args ) { WP_CLI::success( $args[0] ); } if ( class_exists( ‘WP_CLI’ ) ) { WP_CLI::add_command( ‘foo’, ‘foo_command’ ); } This way, the command is only registered when the WP_CLI class exists — because the WP_CLI class will only exist when WP-CLI is running.