What does the "Class not found" exception mean in the context of web-push-php?

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The "Class not found" exception in the context of web-push-php means that the PHP code is attempting to use a class that does not exist or has not been imported/imported correctly. It typically occurs when the code is referencing a class that is misspelled or has a different namespace from the one being used in the PHP script. To resolve this exception, the correct namespace and class name should be used, or the missing class should be imported into the script.