Similar issue to https://www.telerik.com/forums/invalid-classname-diagramconnectiondefaultsendcap-stroke , in the PHP library these files all have invalid classnames (probably autogenerated) :
kendoui\wrappers\php\lib\Kendo\UI\PDFViewerDplProcessing.download.php
kendoui\wrappers\php\lib\Kendo\UI\PDFViewerDplProcessing.read.php
kendoui\wrappers\php\lib\Kendo\UI\PDFViewerDplProcessing.upload.php
These should be deleted, there are correctly name duplicate files for each ( PDFViewerDplProcessingDownload.php , PDFViewerDplProcessingRead.php PDFViewerDplProcessingUpload.php )
I would have done a pull requiest myself, but the PHP library is not a public repository.
This is in the latest version: telerik.ui.for.php.2022.3.1109.commercial