[TYPO3-dev] Quick PHP question

["Christian Müller (FLOW3 Team)"]

On 14/03/12 13:43, Oliver Salzburg wrote:
> I just read the following part in the TYPO3 core API documentation:
>
>> Hooks are the recommended way of extending TYPO3 compared to
>> extending the PHP classes with a child class (see "XCLASS
>> extensions"). It is so because only one extension of a PHP class can
>> exist at a time while hooks may allow many different user-designed
>> processing functions to occur.
>
> The statement "only one extension of a PHP class can exist at a time"
> is really confusing me.
> Was that true at some point in time or did I just skip some important
> pages in my PHP lecture?