SPL的基本使用

SPL是Standard PHP Library（PHP标准库）的缩写。

根据官方定义，它是"a collection of interfaces and classes that are meant to solve standard problems"。但是，目前在使用中，SPL更多地被看作是一种使object（物体）模仿array（数组）行为的interfaces和classes。

这几天学习SPL，这是我写的一点小笔记，望日后再次使用时能够想起点滴，SPL核心便是Iterator，熟练使用Iterator可以让我们更加方便的去操作数据.

ArrayIterator迭代器示例

 <?php
 $fruits = array
 (
     "apple" => 'apple value',
     "orange" => 'orange value',
     "grape" => "grape value",
     "plum" => "plum value"
 );
 print_r($fruits);
 echo "**** use fruits directly\n";
 foreach ($fruits as $key => $value)
 {
     echo $key . ":" . $value . "\n";
 }
 //使用ArrayIterator遍历数组
 $obj = new ArrayObject($fruits);
 $it = $obj->getIterator();

 echo "***** use ArrayIterator in for\n";
 foreach ($it as $key => $value)
 {
     echo $key . ":" . $value . "\n";
 }

 echo "***** use ArrayIterator in while\n";
 $it->rewind();//调用current之前要用rewind
 while ($it->valid())
 {
     echo $it->key() . ":" . $it->current()."\n";
     $it->next();
 }
 //跳过某些元素进行打印
 echo "***** use seek before while\n";
 $it->rewind();
 if ($it->valid())
 {
     $it->seek(1);
     while($it->valid())
     {
         echo $it->key() . ":" . $it->current()."\n";
         $it->next();
     }
 }

 echo "***** use ksort\n";
 $it->ksort();
 foreach ($it as $key => $value)
 {
     echo $key . ":" . $value . "\n";
 }

 echo "***** use asort\n";
 $it->asort();
 foreach ($it as $key => $value)
 {
     echo $key . ":" . $value . "\n";
 }

ArrayIterator

AppendIterator迭代器示例

 <?php
 $array_a = new ArrayIterator(array('a','b','c'));
 $array_b = new ArrayIterator(array('d','e','f'));
 $it = new AppendIterator();
 $it->append($array_a);
 //通过append方法把迭代器对象添加到AppendIterator对象中
 $it->append($array_b);
 foreach ($it as $key => $value)
 {
     echo $value."\n";
 }

AppendIterator

MultipleIterator迭代器示例

 <?php
 $idIter = new ArrayIterator(array('01','02','03'));
 $nameIter = new ArrayIterator(array('张三','李四','王五'));
 $ageIter = new ArrayIterator(array('22','23','25'));
 $mit = new MultipleIterator(MultipleIterator::MIT_KEYS_ASSOC);
 $mit->attachIterator($idIter,"ID");
 $mit->attachIterator($nameIter,"NAME");
 $mit->attachIterator($ageIter,"AGE");
 foreach ($mit as $value)
 {
     print_r($value);
 }

MultipleIterator

FilesystemIterator迭代器示例

 <?php
 $it = new FilesystemIterator('.');
 foreach ($it as $finfo)
 {
     printf("%s\t%s\t%8s\t%s\n",
     date("Y-m-d H:i:s",$finfo->getMTime()),
     $finfo->isDir()?"<DIR>":"",
     number_format($finfo->getSize()),
     $finfo->getFileName()
     );
 }

FilesystemIterator

Countable接口示例

 <?php
 class CountMe implements Countable
 {
     protected $_myCount = 3;
     public function count()
     {
         return $this->_myCount;
     }
 }
 $obj = new CountMe();
 echo count($obj);

Countable

OuterIterator接口示例

 <?php
 $array = ['Value1','Value2','Value3','Value4'];
 $outerObj = new OuterImpl(new ArrayIterator($array));

 foreach ($outerObj as $key => $value)
 {
     echo "++" . $key . " - " . $value . "\n";
 }

 class OuterImpl extends IteratorIterator
 {
     public function current()
     {
         return parent::current()."_tail";
     }
     public function key()
     {
         return "Pre_".parent::key();
     }
 }

OuterIterator

autoload机制的三种用法

 <?php
 //设置autoload寻找php定义的类文件的扩展名,多个扩展名用逗号分隔,前面的扩展名优先被匹配
 spl_autoload_extensions('.class.php,.php');
 //设置autoload寻找php定义的类文件的目录,多个目录用PATH_SEPARATOR进行分隔
 set_include_path(get_include_path().PATH_SEPARATOR."libs/");
 //提示PHP使用Autoload机制查找类定义
 spl_autoload_register();
 new Test();

autoload01

 <?php
 //定义__autoload函数,可以在不调用spl_autoload_register函数的情况完成类的装载
 function __autoload($class_name)
 {
     echo "__autoload class:".$class_name."\n";
     require_once ($class_name.'.php');
 }
 //定义一个替换__autoload函数的类文件装载函数
 function classLoader($class_name)
 {
     echo "classLoader() load class:".$class_name."\n";
     require_once ($class_name.'.php');
 }
 //传入定义好的装载类的函数名称替换__autoload
 spl_autoload_register('classLoader');
 new Test();

autoload02

 <?php

 //定义一个替换__autoload函数的类文件装载函数
 function classLoader($class_name)
 {
     echo "classLoader() load class:".$class_name."\n";
     set_include_path(".");
     spl_autoload($class_name);//当我们不用require或者requir_once载入类文件的时候,而想通过系统查找include_path来装载类是,必须显式调用spl_autoload函数,参数是类的名称来重启类文件的自动查找(装载)
 }
 //传入定义好的装载类的函数名称替换__autoload
 spl_autoload_register('classLoader');
 new Test();

autoload03