+
+/**
+ * Check or set whether WordPress is in "installation" mode.
+ *
+ * If the `WP_INSTALLING` constant is defined during the bootstrap, `wp_installing()` will default to `true`.
+ *
+ * @since 4.4.0
+ *
+ * @staticvar bool $installing
+ *
+ * @param bool $is_installing Optional. True to set WP into Installing mode, false to turn Installing mode off.
+ * Omit this parameter if you only want to fetch the current status.
+ * @return bool True if WP is installing, otherwise false. When a `$is_installing` is passed, the function will
+ * report whether WP was in installing mode prior to the change to `$is_installing`.
+ */
+function wp_installing( $is_installing = null ) {
+ static $installing = null;
+
+ // Support for the `WP_INSTALLING` constant, defined before WP is loaded.
+ if ( is_null( $installing ) ) {
+ $installing = defined( 'WP_INSTALLING' ) && WP_INSTALLING;
+ }
+
+ if ( ! is_null( $is_installing ) ) {
+ $old_installing = $installing;
+ $installing = $is_installing;
+ return (bool) $old_installing;
+ }
+
+ return (bool) $installing;
+}