Some doubts about spl in php?

Why is it specifically called SPL? Why is it not added to PHP like the usual built-in methods of PHP but called SPL, or added as an extension? I have always known that this thing exists, but I didn’t do much research because I felt it was rarely used. However, I actually saw this thing in the framework last week. ~~~

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Why is it specifically called SPL? Why is it not added to PHP like the usual built-in methods of PHP but called SPL, or added as an extension? I have always known that this thing exists, but I didn’t do much research because I felt it was rarely used. However, I actually saw this thing in the framework last week. ~~~

There is nothing special about the name SPL. It is just abbreviated because the full name is Standard PHP Library

It is an extension introduced since PHP 5.0. Of course, it is enabled by default. Starting from 5.3, compilation cannot be canceled. It defines a series of standard data structures, interfaces, etc., and also provides convenient use of PHP's autoload Several methods of the system