search_theme_directories( bool $force = false ): array|false

Searches all registered theme directories for complete and valid themes.

Parameters

$forcebooloptional
Whether to force a new directory scan.

Default:false

Return

array|false Valid themes found on success, false on failure.

Source

function search_theme_directories( $force = false ) {
	global $wp_theme_directories;
	static $found_themes = null;

	if ( empty( $wp_theme_directories ) ) {
		return false;
	}

	if ( ! $force && isset( $found_themes ) ) {
		return $found_themes;
	}

	$found_themes = array();

	$wp_theme_directories = (array) $wp_theme_directories;
	$relative_theme_roots = array();

	/*
	 * Set up maybe-relative, maybe-absolute array of theme directories.
	 * We always want to return absolute, but we need to cache relative
	 * to use in get_theme_root().
	 */
	foreach ( $wp_theme_directories as $theme_root ) {
		if ( str_starts_with( $theme_root, WP_CONTENT_DIR ) ) {
			$relative_theme_roots[ str_replace( WP_CONTENT_DIR, '', $theme_root ) ] = $theme_root;
		} else {
			$relative_theme_roots[ $theme_root ] = $theme_root;
		}
	}

	/**
	 * Filters whether to get the cache of the registered theme directories.
	 *
	 * @since 3.4.0
	 *
	 * @param bool   $cache_expiration Whether to get the cache of the theme directories. Default false.
	 * @param string $context          The class or function name calling the filter.
	 */
	$cache_expiration = apply_filters( 'wp_cache_themes_persistently', false, 'search_theme_directories' );

	if ( $cache_expiration ) {
		$cached_roots = get_site_transient( 'theme_roots' );
		if ( is_array( $cached_roots ) ) {
			foreach ( $cached_roots as $theme_dir => $theme_root ) {
				// A cached theme root is no longer around, so skip it.
				if ( ! isset( $relative_theme_roots[ $theme_root ] ) ) {
					continue;
				}
				$found_themes[ $theme_dir ] = array(
					'theme_file' => $theme_dir . '/style.css',
					'theme_root' => $relative_theme_roots[ $theme_root ], // Convert relative to absolute.
				);
			}
			return $found_themes;
		}
		if ( ! is_int( $cache_expiration ) ) {
			$cache_expiration = 30 * MINUTE_IN_SECONDS;
		}
	} else {
		$cache_expiration = 30 * MINUTE_IN_SECONDS;
	}

	/* Loop the registered theme directories and extract all themes */
	foreach ( $wp_theme_directories as $theme_root ) {

		// Start with directories in the root of the active theme directory.
		$dirs = @ scandir( $theme_root );
		if ( ! $dirs ) {
			trigger_error( "$theme_root is not readable", E_USER_NOTICE );
			continue;
		}
		foreach ( $dirs as $dir ) {
			if ( ! is_dir( $theme_root . '/' . $dir ) || '.' === $dir[0] || 'CVS' === $dir ) {
				continue;
			}
			if ( file_exists( $theme_root . '/' . $dir . '/style.css' ) ) {
				/*
				 * wp-content/themes/a-single-theme
				 * wp-content/themes is $theme_root, a-single-theme is $dir.
				 */
				$found_themes[ $dir ] = array(
					'theme_file' => $dir . '/style.css',
					'theme_root' => $theme_root,
				);
			} else {
				$found_theme = false;
				/*
				 * wp-content/themes/a-folder-of-themes/*
				 * wp-content/themes is $theme_root, a-folder-of-themes is $dir, then themes are $sub_dirs.
				 */
				$sub_dirs = @ scandir( $theme_root . '/' . $dir );
				if ( ! $sub_dirs ) {
					trigger_error( "$theme_root/$dir is not readable", E_USER_NOTICE );
					continue;
				}
				foreach ( $sub_dirs as $sub_dir ) {
					if ( ! is_dir( $theme_root . '/' . $dir . '/' . $sub_dir ) || '.' === $dir[0] || 'CVS' === $dir ) {
						continue;
					}
					if ( ! file_exists( $theme_root . '/' . $dir . '/' . $sub_dir . '/style.css' ) ) {
						continue;
					}
					$found_themes[ $dir . '/' . $sub_dir ] = array(
						'theme_file' => $dir . '/' . $sub_dir . '/style.css',
						'theme_root' => $theme_root,
					);
					$found_theme                           = true;
				}
				/*
				 * Never mind the above, it's just a theme missing a style.css.
				 * Return it; WP_Theme will catch the error.
				 */
				if ( ! $found_theme ) {
					$found_themes[ $dir ] = array(
						'theme_file' => $dir . '/style.css',
						'theme_root' => $theme_root,
					);
				}
			}
		}
	}

	asort( $found_themes );

	$theme_roots          = array();
	$relative_theme_roots = array_flip( $relative_theme_roots );

	foreach ( $found_themes as $theme_dir => $theme_data ) {
		$theme_roots[ $theme_dir ] = $relative_theme_roots[ $theme_data['theme_root'] ]; // Convert absolute to relative.
	}

	if ( get_site_transient( 'theme_roots' ) != $theme_roots ) {
		set_site_transient( 'theme_roots', $theme_roots, $cache_expiration );
	}

	return $found_themes;
}

Hooks

apply_filters( ‘wp_cache_themes_persistently’, bool $cache_expiration, string $context )

Filters whether to get the cache of the registered theme directories.

Changelog

VersionDescription
2.9.0Introduced.

User Contributed Notes

  1. Skip to note 2 content

    The official documentation states that “the style.css file must be located in the root directory of the theme, not in a subdirectory.”. However, looking at the implementation of this function, we can see that this is not true. You can place the style.css and functions.php files in one of direct subdirectories of the root directory. The core will find those files and recognize the subdirectory as the theme’s root directory.

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