Error while cloning a domain in WP Toolkit: Argument #1 ($data) must be of type string, array given

Symptoms

Cloning a domain example.com to clone.example.com in WP Toolkit fails on the Copying databases step with the following error:

PLESK_ERROR: ​”Example” was cloned with errors:
PHP Fatal error: Uncaught TypeError: unserialize(): Argument #1 ($data) must be of type string, array given in /usr/local/psa/admin/plib/modules/wp-toolkit/vendor/wp-cli/vendor/wp-cli/search-replace-command/src/WP_CLI/SearchReplacer.php:86

Cause

PHP 8.0 and WP-CLI compatibility issues.
PHP8 support is planned to be added in a scope of task with ID #EXTWPTOOLK-7619

Resolution

As a workaround:

1. Log in to Plesk

2. Navigate to Domains > clone.example.com > PHP Settings

3. Switch the PHP version from 8.0 to any 7.X handler and press OK to apply the changes

4. Restart the WordPress clone

Note: The cloned domain’s PHP version can be returned, back to 8.0 after the cloning is complete.