[doc] Update PHP doc links (#18957)

* Replace https://secure.php.net with https://www.php.net

* Replace http://www.php.net with https://www.php.net

docs/guide/tutorial-core-validators.md

@@ -141,7 +141,7 @@ specified via [[yii\validators\DateValidator::timestampAttribute|timestampAttrib
 - `format`: the date/time format that the value being validated should be in.
    This can be a date time pattern as described in the [ICU manual](http://userguide.icu-project.org/formatparse/datetime#TOC-Date-Time-Format-Syntax).
    Alternatively this can be a string prefixed with `php:` representing a format that can be recognized by the PHP
-   `Datetime` class. Please refer to <https://secure.php.net/manual/en/datetime.createfromformat.php> on supported formats.
+   `Datetime` class. Please refer to <https://www.php.net/manual/en/datetime.createfromformat.php> on supported formats.
    If this is not set, it will take the value of `Yii::$app->formatter->dateFormat`.
    See the [[yii\validators\DateValidator::$format|API documentation]] for more details.
 
@@ -424,8 +424,8 @@ back to the attribute being validated.
 > Tip: If you want to trim input values, you may directly use the [trim](#trim) validator.
 
 > Tip: There are many PHP functions that have the signature expected for the `filter` callback.
-> For example to apply type casting (using e.g. [intval](https://secure.php.net/manual/en/function.intval.php),
-> [boolval](https://secure.php.net/manual/en/function.boolval.php), ...) to ensure a specific type for an attribute,
+> For example to apply type casting (using e.g. [intval](https://www.php.net/manual/en/function.intval.php),
+> [boolval](https://www.php.net/manual/en/function.boolval.php), ...) to ensure a specific type for an attribute,
 > you can simply specify the function names of the filter without the need to wrap them in a closure:
 >
 > ```php