Options, Meta APIs: Fix "passing null to non-nullable" deprecations to `(get|add|update|delete)_option()`.

In all four of the `get_option()`, `add_option()`, `update_option()` and `delete_option()` functions, the `$option` parameter (i.e. the option name) is passed to the PHP native `trim()` function without prior input validation.

In PHP 8.1, this could lead to a `trim(): Passing null to parameter #1 ($string) of type string is deprecated` for each of these functions.

`trim()`:

- expects a text string and is only useful when ''passed'' a text string as no other variable type can contain whitespace.
- will always return a `string`, which means that in practice for any non-string values passed, it would effectively function as a type cast to string.

This commit:
- Adds a check to verify the `$option` name is a scalar before processing it with `trim()`.
- The "type cast" behavior is maintained.
- If the given `$option` name is not a scalar, such as `null`, the fix prevents the PHP 8.1 deprecation notice.
- Tests are added for valid but undesired option names to safeguard against regressions.

This issue is already covered by:
- the existing `Tests_Option_Option::test_bad_option_names()` test group.
- the new `test_valid_but_undesired_option_names()` tests.

Follow-up to [13858], [22633], [23510], [25002], [51817].

Props jrf, hellofromTonya, pbearne.
See #53635.
Built from https://develop.svn.wordpress.org/trunk@51818


git-svn-id: http://core.svn.wordpress.org/trunk@51425 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/option.php

@@ -77,7 +77,10 @@
 function get_option( $option, $default = false ) {
 	global $wpdb;
 
+	if ( is_scalar( $option ) ) {
 		$option = trim( $option );
+	}
+
 	if ( empty( $option ) ) {
 		return false;
 	}
@@ -378,7 +381,10 @@ function wp_load_core_site_options( $network_id = null ) {
 function update_option( $option, $value, $autoload = null ) {
 	global $wpdb;
 
+	if ( is_scalar( $option ) ) {
 		$option = trim( $option );
+	}
+
 	if ( empty( $option ) ) {
 		return false;
 	}
@@ -565,7 +571,10 @@ function add_option( $option, $value = '', $deprecated = '', $autoload = 'yes' )
 		_deprecated_argument( __FUNCTION__, '2.3.0' );
 	}
 
+	if ( is_scalar( $option ) ) {
 		$option = trim( $option );
+	}
+
 	if ( empty( $option ) ) {
 		return false;
 	}
@@ -687,7 +696,10 @@ function add_option( $option, $value = '', $deprecated = '', $autoload = 'yes' )
 function delete_option( $option ) {
 	global $wpdb;
 
+	if ( is_scalar( $option ) ) {
 		$option = trim( $option );
+	}
+
 	if ( empty( $option ) ) {
 		return false;
 	}

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51817';
+$wp_version = '5.9-alpha-51818';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.