Docs: Correct documentation for current_time(), date_i18n(), and wp_date().

Includes:
* Standardizing on the `bool` type for the `$gmt` parameter between `current_time()` and `date_i18n()`.
* Documenting `null` as an acceptable value for `$timestamp` and `$timezone` parameters in `wp_date()`.
* Removing a redundant note on the `$gmt` parameter for the `date_i18n` filter, as defaults are normally only documented for function parameters.

Follow-up to [1001], [9616], [28109], [45901].

Props dilipbheda.
Fixes #63207.

git-svn-id: https://develop.svn.wordpress.org/trunk@60119 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-includes/functions.php

@@ -70,12 +70,12 @@ function mysql2date( $format, $date, $translate = true ) {
  * @since 1.0.0
  * @since 5.3.0 Now returns an integer if `$type` is 'U'. Previously a string was returned.
  *
- * @param string   $type Type of time to retrieve. Accepts 'mysql', 'timestamp', 'U',
- *                       or PHP date format string (e.g. 'Y-m-d').
- * @param int|bool $gmt  Optional. Whether to use GMT timezone. Default false.
+ * @param string $type Type of time to retrieve. Accepts 'mysql', 'timestamp', 'U',
+ *                     or PHP date format string (e.g. 'Y-m-d').
+ * @param bool   $gmt  Optional. Whether to use GMT timezone. Default false.
  * @return int|string Integer if `$type` is 'timestamp' or 'U', string otherwise.
  */
-function current_time( $type, $gmt = 0 ) {
+function current_time( $type, $gmt = false ) {
 	// Don't use non-GMT timestamp, unless you know the difference and really need to.
 	if ( 'timestamp' === $type || 'U' === $type ) {
 		return $gmt ? time() : time() + (int) ( (float) get_option( 'gmt_offset' ) * HOUR_IN_SECONDS );
@@ -216,7 +216,6 @@ function date_i18n( $format, $timestamp_with_offset = false, $gmt = false ) {
 	 * @param int    $timestamp A sum of Unix timestamp and timezone offset in seconds.
 	 *                          Might be without offset if input omitted timestamp but requested GMT.
 	 * @param bool   $gmt       Whether to use GMT timezone. Only applies if timestamp was not provided.
-	 *                          Default false.
 	 */
 	$date = apply_filters( 'date_i18n', $date, $format, $timestamp, $gmt );
 
@@ -235,10 +234,10 @@ function date_i18n( $format, $timestamp_with_offset = false, $gmt = false ) {
  *
  * @global WP_Locale $wp_locale WordPress date and time locale object.
  *
- * @param string       $format    PHP date format.
- * @param int          $timestamp Optional. Unix timestamp. Defaults to current time.
- * @param DateTimeZone $timezone  Optional. Timezone to output result in. Defaults to timezone
- *                                from site settings.
+ * @param string            $format    PHP date format.
+ * @param int|null          $timestamp Optional. Unix timestamp. Defaults to current time.
+ * @param DateTimeZone|null $timezone  Optional. Timezone to output result in. Defaults to timezone
+ *                                     from site settings.
  * @return string|false The date, translated if locale specifies it. False on invalid timestamp input.
  */
 function wp_date( $format, $timestamp = null, $timezone = null ) {