feat(PHP): add deleteFolderRecursive sample

[nidhiii-27]

This adds a sample demonstrating how to recursively delete a folder in a hierarchical namespace bucket.

Fixes: b/521168740

[snippet-bot]

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• storagecontrol/src/delete_folder_recursive.php:26, tag storage_control_delete_folder_recursive

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[gemini-code-assist]

Code Review

This pull request introduces a new PHP sample, delete_folder_recursive.php, which demonstrates how to recursively delete a folder and its contents in Cloud Storage, along with an integration test in StorageControlTest.php. The reviewer suggested a defensive programming improvement to ensure $operation->getError() is not null before calling getMessage(), preventing potential runtime errors if the error object is missing.

[gemini-code-assist]

To prevent potential null pointer/member function call on null errors, it is safer to check if $operation->getError() is not null before calling getMessage(). Although an error is expected when operationSucceeded() is false, defensive programming ensures robustness against unexpected API response formats.

    } else {
        $error = $operation->getError();
        printf('Failed to delete folder: %s', $error ? $error->getMessage() : 'Unknown error');
    }

[nidhiii-27]

Done