PHP 8.1: Passing `null` to non-nullable parameters of built-in functions

[ethanclevenger91]

Description of Problem

PHP deprecation message:

PHP Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in xxxxxxxxxxxxxxxx\wp-content\plugins\simple-lightbox\includes\class.utilities.php on line 545

In the WP.org support post you mentioned this seemed like a configuration problem, because null shouldn't be what gets passed around there. But you do have code explicitly setting this var to null in some scenarios. I've added some comments to the below source code identifying such instances:

function extend_client_object( $obj, $data = null, $out = false ) {
		// Validate parameters
		$args = func_get_args();
		switch ( count( $args ) ) {
			case 2:
				if ( ! is_scalar( $args[0] ) ) {
					if ( is_bool( $args[1] ) ) {
						$out = $args[1];
					}
				} else {
					break;
				}
				// no break.
			case 1:
                                // HERE
				$data = $args[0];
				$obj  = null;
				break;
		}
		// Default client object
		if ( ! is_string( $obj ) || empty( $obj ) ) {
                        // AND HERE
			$obj = null;
		}
		// Default data
		if ( is_array( $data ) ) {
			$data = (object) $data;
		}
		// Build expression
		if ( empty( $data ) || ( empty( $obj ) && is_scalar( $data ) ) ) {
			$ret = '';
		} else {
			$c_obj = $this->get_client_object( $obj );
                        // Then it's passed to `validate_client_object`, which is where it gets passed to `trim` in such a way that PHP 8.1 doesn't like.
			$ret   = $this->validate_client_object( $obj, sprintf( '{$.extend(%1$s, %2$s);}', $c_obj, wp_json_encode( $data ) ) );
			if ( $out ) {
                        // so on and so forth

Maybe that could either default to something valid for the call to trim or short-circuit or...idk. Something else.

Details

• URL of Page exhibiting problem: dev environment, but message is appearing at bottom of admin pages and front-end pages
• Browser(s) exhibiting problem (Firefox, Chrome, etc.): Firefox
• Version of SLB Installed: 2.9.3
• Other plugins installed:

+---------------------------------+----------+--------+---------+
| name                            | status   | update | version |
+---------------------------------+----------+--------+---------+
| advanced-custom-fields-pro      | active   | none   | 6.1.4   |
| sterner-stuff-barncraft         | active   | none   |         |
| easy-notification-bar           | inactive | none   | 1.4.5   |
| font-awesome                    | active   | none   | 4.3.2   |
| gravityforms                    | active   | none   | 2.7.4   |
| gravityformscli                 | active   | none   | 1.4     |
| gravityformspartialentries      | active   | none   | 1.7     |
| gravity-forms-zero-spam         | active   | none   | 1.4     |
| gutenberg                       | active   | none   | 15.6.2  |
| mailgun                         | active   | none   | 1.9.3   |
| redirection                     | active   | none   | 5.3.10  |
| safe-svg                        | active   | none   | 2.1.1   |
| simple-lightbox                 | active   | none   | 2.9.3   |
| google-site-kit                 | active   | none   | 1.99.0  |
| stream                          | active   | none   | 3.9.3   |
| tiny-compress-images            | active   | none   | 3.4.1   |
| wp-crontrol                     | active   | none   | 1.15.2  |
| wp-migrate-db-pro               | active   | none   | 2.6.5   |
| amazon-s3-and-cloudfront-pro    | active   | none   | 3.2.1   |
| wp-rocket                       | active   | none   | 3.13.1  |
| wordpress-seo                   | active   | none   | 20.6    |
| zero-spam                       | active   | none   | 5.4.4   |
| bedrock-autoloader              | must-use | none   | 1.0.3   |
| wp-migrate-db-pro-compatibility | must-use | none   | 1.3     |
| advanced-cache.php              | dropin   | none   |         |
+---------------------------------+----------+--------+---------+