SPL is a collection of interfaces and classes that are meant to solve standard problems.
A more detailed documentation of SPL can be found » here.
This extension is available and compiled by default in PHP 5.
以下常數由擴充功能定義,因此只有在擴充功能被編譯到 PHP 中,或者在執行時被動態載入後才有效。
SPL uses class constants since PHP 5.1. Prior releases use global constants in the form RIT_LEAVES_ONLY.