wp_salt( string $scheme = 'auth' ): string

2585	function wp_salt( $scheme = 'auth' ) {2586		static $cached_salts = array();2587		if ( isset( $cached_salts[ $scheme ] ) ) {2588			/**2589			 * Filters the WordPress salt.2590			 *2591			 * @since 2.5.02592			 *2593			 * @param string $cached_salt Cached salt for the given scheme.2594			 * @param string $scheme      Authentication scheme. Values include 'auth',2595			 *                            'secure_auth', 'logged_in', and 'nonce'.2596			 */2597			return apply_filters( 'salt', $cached_salts[ $scheme ], $scheme );2598		}2599 2600		static $duplicated_keys;2601		if ( null === $duplicated_keys ) {2602			$duplicated_keys = array();2603 2604			foreach ( array( 'AUTH', 'SECURE_AUTH', 'LOGGED_IN', 'NONCE', 'SECRET' ) as $first ) {2605				foreach ( array( 'KEY', 'SALT' ) as $second ) {2606					if ( ! defined( "{$first}_{$second}" ) ) {2607						continue;2608					}2609					$value                     = constant( "{$first}_{$second}" );2610					$duplicated_keys[ $value ] = isset( $duplicated_keys[ $value ] );2611				}2612			}2613 2614			$duplicated_keys['put your unique phrase here'] = true;2615 2616			/*2617			 * translators: This string should only be translated if wp-config-sample.php is localized.2618			 * You can check the localized release package or2619			 * https://i18n.svn.wordpress.org/<locale code>/branches/<wp version>/dist/wp-config-sample.php2620			 */2621			$duplicated_keys[ __( 'put your unique phrase here' ) ] = true;2622		}2623 2624		/*2625		 * Determine which options to prime.2626		 *2627		 * If the salt keys are undefined, use a duplicate value or the2628		 * default `put your unique phrase here` value the salt will be2629		 * generated via `wp_generate_password()` and stored as a site2630		 * option. These options will be primed to avoid repeated2631		 * database requests for undefined salts.2632		 */2633		$options_to_prime = array();2634		foreach ( array( 'auth', 'secure_auth', 'logged_in', 'nonce' ) as $key ) {2635			foreach ( array( 'key', 'salt' ) as $second ) {2636				$const = strtoupper( "{$key}_{$second}" );2637				if ( ! defined( $const ) || true === $duplicated_keys[ constant( $const ) ] ) {2638					$options_to_prime[] = "{$key}_{$second}";2639				}2640			}2641		}2642 2643		if ( ! empty( $options_to_prime ) ) {2644			/*2645			 * Also prime `secret_key` used for undefined salting schemes.2646			 *2647			 * If the scheme is unknown, the default value for `secret_key` will be2648			 * used too for the salt. This should rarely happen, so the option is only2649			 * primed if other salts are undefined.2650			 *2651			 * At this point of execution it is known that a database call will be made2652			 * to prime salts, so the `secret_key` option can be primed regardless of the2653			 * constants status.2654			 */2655			$options_to_prime[] = 'secret_key';2656			wp_prime_site_option_caches( $options_to_prime );2657		}2658 2659		$values = array(2660			'key'  => '',2661			'salt' => '',2662		);2663		if ( defined( 'SECRET_KEY' ) && SECRET_KEY && empty( $duplicated_keys[ SECRET_KEY ] ) ) {2664			$values['key'] = SECRET_KEY;