Update src/Theme_Cache_Command.php

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: swissspidy

src/Theme_Cache_Command.php

@@ -99,8 +99,20 @@ public function flush( $args, $assoc_args ) {
 		// Only added in WordPress 6.1.
 		if ( function_exists( 'wp_cache_flush_group' ) ) {
 			wp_cache_flush_group( 'themes' );
+			WP_CLI::success( 'The theme cache was flushed.' );
+			return;
+		}
+
+		// Fallback for WordPress versions prior to 6.1: clear cache for all themes.
+		if ( function_exists( 'wp_get_themes' ) ) {
+			$all_themes = wp_get_themes();
+			foreach ( $all_themes as $theme ) {
+				$this->clear_theme_cache( $theme );
+			}
+			WP_CLI::success( 'The theme cache was flushed.' );
+		} else {
+			WP_CLI::warning( 'Your WordPress version does not support flushing the theme cache group.' );
 		}
-		WP_CLI::success( 'The theme cache was flushed.' );
 	}
 
 	/**