spl 是什麼
* SPL是Standard
PHP Library（PHP標準庫）的縮寫。
* 根據官方定義，它是“a collection of interfaces and classes that are meant tosolve standard problems
* 目前在使用中，SPL更多地被看作是一種使object（物體）模仿array（數組）行爲的interfaces和classes。
spl可以幹什麼用
/**
* spl 作用
* （1） 提供了一系列的標準的數據機構
SplDoublyLinkedList — The SplDoublyLinkedList class
SplStack — The SplStack class
SplQueue — The SplQueue class
SplHeap — The SplHeap class
SplMaxHeap — The SplMaxHeap class
SplMinHeap — The SplMinHeap class
SplPriorityQueue — The SplPriorityQueue class
SplFixedArray — The SplFixedArray class
SplObjectStorage — The SplObjectStorage class
* （2） 提供了一系列迭代器
AppendIterator — The AppendIterator class
ArrayIterator — The ArrayIterator class
CachingIterator — The CachingIterator class
CallbackFilterIterator — The CallbackFilterIterator class
DirectoryIterator — The DirectoryIterator class
EmptyIterator — The EmptyIterator class
FilesystemIterator — The FilesystemIterator class
FilterIterator — The FilterIterator class
GlobIterator — The GlobIterator class
InfiniteIterator — The InfiniteIterator class
IteratorIterator — The IteratorIterator class
LimitIterator — The LimitIterator class
MultipleIterator — The MultipleIterator class
NoRewindIterator — The NoRewindIterator class
ParentIterator — The ParentIterator class
RecursiveArrayIterator — The RecursiveArrayIterator class
RecursiveCachingIterator — The RecursiveCachingIterator class
RecursiveCallbackFilterIterator — The RecursiveCallbackFilterIterator class
RecursiveDirectoryIterator — The RecursiveDirectoryIterator class
RecursiveFilterIterator — The RecursiveFilterIterator class
RecursiveIteratorIterator — The RecursiveIteratorIterator class
RecursiveRegexIterator — The RecursiveRegexIterator class
RecursiveTreeIterator — The RecursiveTreeIterator class
RegexIterator — The RegexIterator class
*
*
* （3） 提供了一系列接口
Countable — The Countable interface
OuterIterator — The OuterIterator interface
RecursiveIterator — The RecursiveIterator interface
SeekableIterator — The SeekableIterator interface
* （4） 提供了一系列標準異常
BadFunctionCallException — The BadFunctionCallException class
BadMethodCallException — The BadMethodCallException class
DomainException — The DomainException class
InvalidArgumentException — The InvalidArgumentException class
LengthException — The LengthException class
LogicException — The LogicException class
OutOfBoundsException — The OutOfBoundsException class
OutOfRangeException — The OutOfRangeException class
OverflowException — The OverflowException class
RangeException — The RangeException class
RuntimeException — The RuntimeException class
UnderflowException — The UnderflowException class
UnexpectedValueException — The UnexpectedValueException class
* (5) 一系列方法
class_implements — Return the interfaces which are implemented by the given class or interface
class_parents — Return the parent classes of the given class
class_uses — Return the traits used by the given class
iterator_apply — Call a function for every element in an iterator
iterator_count — Count the elements in an iterator
iterator_to_array — Copy the iterator into an array
spl_autoload_call — Try all registered __autoload() function to load the requested class
spl_autoload_extensions — Register and return default file extensions for spl_autoload
spl_autoload_functions — Return all registered __autoload() functions
spl_autoload_register — Register given function as __autoload() implementation
spl_autoload_unregister — Unregister given function as __autoload() implementation
spl_autoload — Default implementation for __autoload()
spl_classes — Return available SPL classes
spl_object_hash — Return hash id for given object
*
*
*/