Wp CLI Extending

WP-CLI: Extending with Custom Commands

WP-CLI is the maintenance / automation interface to a WordPress install. Almost no plugin ships CLI commands — even though wp myplugin import, wp myplugin clear-cache, wp myplugin run-sync are exactly what ops people want. The API is WP_CLI::add_command() and a class with PHPDoc-annotated methods.

When to use this skill

Trigger when ANY of the following is true:

• A plugin needs a CLI surface — bulk import / export, data migration, queue dispatch, debug introspection, scheduled-job force-run, cache clear, license activate.
• Code references WP_CLI::add_command, WP_CLI::log, WP_CLI::success, WP_CLI::warning, WP_CLI::error, WP_CLI::confirm, WP_CLI::runcommand, WP_CLI::add_hook, WP_CLI\Utils\format_items, WP_CLI\Utils\make_progress_bar, WP_CLI\Utils\get_flag_value.
• The user has a long-running admin task (update_option loop over 50k rows, AJAX-timing-out import) and wants to run it from terminal.
• Code is checking if ( defined( 'WP_CLI' ) && WP_CLI ) and the body is empty / wrong.

The bootstrap — guard, then register

// In the plugin's main file or a dedicated CLI bootstrap.
if ( defined( 'WP_CLI' ) && WP_CLI ) {
    WP_CLI::add_command( 'myplugin', MyPlugin\CLI\Commands::class );
}

The class is instantiated lazily when WP-CLI dispatches a myplugin ... invocation. PHPDoc on each method is what drives synopsis / help. Public methods become subcommands. Method names are used as-is, so import_licenses registers wp myplugin import_licenses unless you add @subcommand import-licenses. Use @subcommand for normal hyphenated command names.

Full worked example (import + list with progress bar, dry-run, format args) lives in reference.md. The skeleton:

namespace MyPlugin\CLI;

final class Commands {
    /**
     * One-line description.
     *
     * ## OPTIONS
     *
     * <file>
     * : Positional, required.
     *
     * [--dry-run]
     * : Optional flag.
     *
     * @subcommand import-licenses
     * @when after_wp_load
     */
    public function import_licenses( array $args, array $assoc_args ): void {
        [ $file ] = $args;
        $dry = (bool) \WP_CLI\Utils\get_flag_value( $assoc_args, 'dry-run', false );
        // ... work, with \WP_CLI::log() / success() / error() ...
    }
}

PHPDoc drives the synopsis — get the format right

WP-CLI parses the docblock for command help / arg validation. The strict format:

The arg pattern lines are NOT freeform — they MUST match WP-CLI's parser. Run wp help myplugin import-licenses to see what the parser made of your docblock; if the command is missing, check the method name / @subcommand tag first. If the ## OPTIONS section looks wrong there, the docblock is malformed.

I/O helpers — pick the right severity

Verified at WP_CLI class methods (reflection-confirmed):

\WP_CLI::line( $msg );           // plain stdout; no log prefix
\WP_CLI::log( $msg );            // also plain stdout but suppressed by --quiet
\WP_CLI::success( $msg );        // green "Success: ..."
\WP_CLI::warning( $msg );        // yellow "Warning: ..."
\WP_CLI::error( $msg, true );    // red "Error: ..." AND exit non-zero (default)
\WP_CLI::error( $msg, false );   // print error but continue
\WP_CLI::debug( $msg );          // only printed with --debug flag
\WP_CLI::confirm( $question, $assoc_args ); // y/n prompt; auto-yes when $assoc_args contains --yes
\WP_CLI::halt( $code );          // exit with custom code

error exits by default — use it for "abort the command". warning does not exit.

Formatted output — match the --format convention

Every WP-CLI command that lists data accepts --format=<table|csv|json|yaml|count>. Build your commands the same way. WP_CLI\Utils\format_items( $format, $items, $fields ) does the work (signature verified via reflection).

$format = \WP_CLI\Utils\get_flag_value( $assoc_args, 'format', 'table' );
\WP_CLI\Utils\format_items( $format, $items, array( 'id', 'name', 'expires_at' ) );

Declare the format enum in the PHPDoc with the --- YAML-block syntax so WP-CLI validates user input — full example in reference.md:

 * [--format=<format>]
 * : Output format.
 * ---
 * default: table
 * options:
 *   - table
 *   - csv
 *   - json
 *   - yaml
 *   - count
 * ---

Invoking other commands — runcommand

Reflection-confirmed signature: WP_CLI::runcommand( $command, $options = [] ). Options:

// Run another command and capture its JSON output.
$users = \WP_CLI::runcommand( 'user list --role=customer --format=json', array(
    'return' => true,
    'parse'  => 'json',
) );

// Fire-and-forget; let it print to terminal.
\WP_CLI::runcommand( 'cache flush' );

Lifecycle hooks — WP_CLI::add_hook

Useful for plugins that need to run init logic before/after specific commands, or before WP loads at all:

WP_CLI::add_hook( 'before_invoke:myplugin import-licenses', static function () {
    \WP_CLI::log( 'Disabling Action Scheduler runners for the import...' );
    remove_action( 'action_scheduler_run_queue', 'ActionScheduler::run_queue' );
} );

Long-running commands and progress bars

WP_CLI\Utils\make_progress_bar( $message, $count, $interval = 100 ) returns a progress bar (\cli\progress\Bar from the wp-cli/php-cli-tools lib). Call ->tick() (with optional increment) per item, ->finish() at the end.

$bar = \WP_CLI\Utils\make_progress_bar( 'Migrating', $total );
foreach ( $rows as $row ) {
    migrate_one( $row );
    $bar->tick();
}
$bar->finish();

For commands that take >30 seconds, flush WP object cache between batches and wp_get_db_schema()-style commands — the persistent $wpdb accumulates query log + cached results. Common pattern:

foreach ( array_chunk( $ids, 500 ) as $chunk ) {
    process_chunk( $chunk );
    \WP_CLI\Utils\wp_clear_object_cache();  // utility function, reflection-confirmed
}

Critical rules

• Always guard registration with defined( 'WP_CLI' ) && WP_CLI. Otherwise the WP_CLI::add_command call fatals on every web request — the class doesn't exist outside CLI runs.
• Method visibility matters. Only public methods are exposed as subcommands. protected / private helpers don't leak — use them freely.
• Underscores are not automatically converted to hyphens. A method named import_licenses registers as import_licenses; add @subcommand import-licenses when the CLI command should be hyphenated.
• Register a class name, not an already-instantiated object, when you want lazy loading. With a class string, WP-CLI reflects PHPDoc during registration/help and only constructs the class when the command is invoked. Constructors should still stay cheap because every real command run pays for them.
• @when after_wp_load is the default. Only use @when before_wp_load for genuinely WP-independent commands (config inspection, file scaffolding). Most plugin commands need WP loaded.
• WP_CLI::error() exits with non-zero by default. Pass false as the 2nd arg only when you genuinely want to print "Error:" but continue.
• Format your output via WP_CLI\Utils\format_items(), not by echo. Users expect --format=json to work; rolling your own table breaks pipelines and scripts.
• Don't bypass WP_CLI::log with raw echo. echo doesn't respect --quiet; logs always do.
• Pass $assoc_args to WP_CLI::confirm() when you want --yes support. Calling confirm( $question ) prompts even if the user supplied --yes.
• Don't query the database from before_wp_load. $wpdb is not initialized yet. Use after_wp_load (the default) for anything touching WP state.
• Don't wp_die() inside a CLI command — it bypasses WP-CLI's error formatting and produces ugly stack traces. Use WP_CLI::error().

Common AI mistakes

See reference.md for before/after snippets covering: missing defined('WP_CLI') guard, hand-rolled synopsis logic instead of PHPDoc, raw echo instead of WP_CLI::log/success/error, hand-built tables that break --format=json, and wp_die() inside a CLI command.

Cross-references

• See wp-plugin-cron when the CLI command's job is to dispatch background work — Action Scheduler / cron is the right destination, not "do it all in the CLI invocation".
• See wp-rest-api when the same logic also needs a REST surface — extract the core into a service class, expose via both CLI command and REST route.
• See wp-locale-and-dates for wp_date() output in command tables — locale-aware display matters in --format=table.

What this skill does NOT cover

• Distributing the command as a standalone WP-CLI package (composer.json, wp package install). Plugin-shipped commands cover 95% of plugin needs.
• Writing your own custom output formatter (subclassing WP_CLI\Formatter). Almost never needed — format_items covers everything.
• The package authoring conventions (wp-cli/dotenv-command style). Out of scope.

References

• WP_CLI::add_command() — reflection-verified signature add_command( $name, $callable, $args = [] ).
• WP_CLI\Utils\format_items() — reflection-verified format_items( $format, $items, $fields ).
• WP_CLI\Utils\make_progress_bar() — reflection-verified make_progress_bar( $message, $count, $interval = 100 ).
• WP_CLI\Utils\get_flag_value() — get_flag_value( $assoc_args, $flag, $default = null ).
• WP-CLI handbook (canonical docs): https://make.wordpress.org/cli/handbook/references/internal-api/
• WP-CLI hook system: https://make.wordpress.org/cli/handbook/guides/hook-system/