PHP SPL 筆記
這幾天，我在學習PHP語言中的SPL。php
這個東西應該屬於PHP中的高級內容，看上去很複雜，可是很是有用，因此我作了長篇筆記。否則記不住，之後要用的時候，仍是要從頭學起。html
因爲這是供本身參考的筆記，不是教程，因此寫得比較簡單，沒有多解釋。可是我想，若是你是一個熟練的PHP5程序員，應該足以看懂下面的材料，並且會發現它頗有用。如今除此以外，網上根本沒有任何深刻的SPL中文介紹。node
===============================mysql
第一部 簡介
一、什麼是SPL？
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 to solve standard problems"。可是，目前在使用中，SPL更多地被看做是一種使object（物體）模仿array（數組）行爲的interfaces和classes。程序員
二、什麼是Iterator？
SPL的核心概念就是Iterator。通俗地說，Iterator可以使許多不一樣的數據結構，都能有統一的操做界面，好比一個數據庫的結果集、同一個目錄中的文件集、或者一個文本中每一行構成的集合。
若是按照普通狀況，遍歷一個MySQL的結果集，程序須要這樣寫：web
// Fetch the "aggregate structure"
$result = mysql_query("SELECT * FROM users");
// Iterate over the structure
while ( $row = mysql_fetch_array($result) ) {
// do stuff with the row here
}
讀出一個目錄中的內容，須要這樣寫：sql
// Fetch the "aggregate structure"
$dh = opendir('/home/harryf/files');
// Iterate over the structure
while ( $file = readdir($dh) ) {
// do stuff with the file here
}
讀出一個文本文件的內容，須要這樣寫：數據庫
// Fetch the "aggregate structure"
$dh = opendir('/home/harryf/files');
// Iterate over the structure
while ( $file = readdir($dh) ) {
// do stuff with the file here
}
上面三段代碼，雖然處理的是不一樣的resource（資源），可是功能都是遍歷結果集（loop over contents），所以Iterator的基本思想，就是將這三種不一樣的操做統一塊兒來，用一樣的命令界面，處理不一樣的資源。apache
第二部分 SPL Interfaces
三、Iterator 接口
SPL規定，全部部署了Iterator界面的class，均可以用在foreach Loop中。Iterator界面中包含5個必須部署的方法：
* current()
This method returns the current index's value. You are solely
responsible for tracking what the current index is as the
interface does not do this for you.
* key()
This method returns the value of the current index's key. For
foreach loops this is extremely important so that the key
value can be populated.
* next()
This method moves the internal index forward one entry.
* rewind()
This method should reset the internal index to the first element.
* valid()
This method should return true or false if there is a current
element. It is called after rewind() or next().
下面就是一個部署了Iterator界面的class示例：編程
/**
* An iterator for native PHP arrays, re-inventing the wheel
*
* Notice the "implements Iterator" - important!
*/
class ArrayReloaded implements Iterator {
/**
* A native PHP array to iterate over
*/
private $array = array();
/**
* A switch to keep track of the end of the array
*/
private $valid = FALSE;
/**
* Constructor
* @param array native PHP array to iterate over
*/
function __construct($array) {
$this->array = $array;
}
/**
* Return the array "pointer" to the first element
* PHP's reset() returns false if the array has no elements
*/
function rewind(){
$this->valid = (FALSE !== reset($this->array));
}
/**
* Return the current array element
*/
function current(){
return current($this->array);
}
/**
* Return the key of the current array element
*/
function key(){
return key($this->array);
}
/**
* Move forward by one
* PHP's next() returns false if there are no more elements
*/
function next(){
$this->valid = (FALSE !== next($this->array));
}
/**
* Is the current element valid?
*/
function valid(){
return $this->valid;
}
}
使用方法以下：
// Create iterator object
$colors = new ArrayReloaded(array ('red','green','blue',));
// Iterate away!
foreach ( $colors as $color ) {
echo $color."<br>";
}
你也能夠在foreach循環中使用key()方法：
// Display the keys as well
foreach ( $colors as $key => $color ) {
echo "$key: $color<br>";
}
除了foreach循環外，也可使用while循環，
// Reset the iterator - foreach does this automatically
$colors->rewind();
// Loop while valid
while ( $colors->valid() ) {
echo $colors->key().": ".$colors->current()."
";
$colors->next();
}
根據測試，while循環要稍快於foreach循環，由於運行時少了一層中間調用。
四、ArrayAccess接口
部署ArrayAccess界面，可使得object像array那樣操做。ArrayAccess界面包含四個必須部署的方法：
* offsetExists($offset)
This method is used to tell php if there is a value
for the key specified by offset. It should return
true or false.
* offsetGet($offset)
This method is used to return the value specified
by the key offset.
* offsetSet($offset, $value)
This method is used to set a value within the object,
you can throw an exception from this function for a
read-only collection.
* offsetUnset($offset)
This method is used when a value is removed from
an array either through unset() or assigning the key
a value of null. In the case of numerical arrays, this
offset should not be deleted and the array should
not be reindexed unless that is specifically the
behavior you want.
下面就是一個部署ArrayAccess界面的實例：
/**
* A class that can be used like an array
*/
class Article implements ArrayAccess {
public $title;
public $author;
public $category;
function __construct($title,$author,$category) {
$this->title = $title;
$this->author = $author;
$this->category = $category;
}
/**
* Defined by ArrayAccess interface
* Set a value given it's key e.g. $A['title'] = 'foo';
* @param mixed key (string or integer)
* @param mixed value
* @return void
*/
function offsetSet($key, $value) {
if ( array_key_exists($key,get_object_vars($this)) ) {
$this->{$key} = $value;
}
}
/**
* Defined by ArrayAccess interface
* Return a value given it's key e.g. echo $A['title'];
* @param mixed key (string or integer)
* @return mixed value
*/
function offsetGet($key) {
if ( array_key_exists($key,get_object_vars($this)) ) {
return $this->{$key};
}
}
/**
* Defined by ArrayAccess interface
* Unset a value by it's key e.g. unset($A['title']);
* @param mixed key (string or integer)
* @return void
*/
function offsetUnset($key) {
if ( array_key_exists($key,get_object_vars($this)) ) {
unset($this->{$key});
}
}
/**
* Defined by ArrayAccess interface
* Check value exists, given it's key e.g. isset($A['title'])
* @param mixed key (string or integer)
* @return boolean
*/
function offsetExists($offset) {
return array_key_exists($offset,get_object_vars($this));
}
}
使用方法以下：
// Create the object
$A = new Article('SPL Rocks','Joe Bloggs', 'PHP');
// Check what it looks like
echo 'Initial State:<div>';
print_r($A);
echo '</div>';
// Change the title using array syntax
$A['title'] = 'SPL _really_ rocks';
// Try setting a non existent property (ignored)
$A['not found'] = 1;
// Unset the author field
unset($A['author']);
// Check what it looks like again
echo 'Final State:<div>';
print_r($A);
echo '</div>';
運行結果以下：
Initial State: Article Object ( [title] => SPL Rocks [author] => Joe Bloggs [category] => PHP ) Final State: Article Object ( [title] => SPL _really_ rocks [category] => PHP )
能夠看到，$A雖然是一個object，可是徹底能夠像array那樣操做。
你還能夠在讀取數據時，增長程序內部的邏輯：
function offsetGet($key) {
if ( array_key_exists($key,get_object_vars($this)) ) {
return strtolower($this->{$key});
}
}
五、IteratorAggregate 接口
雖然$A能夠像數組那樣操做，卻沒法使用foreach遍歷，除非部署了前面提到的Iterator界面。
另外一個解決方法是，有時會須要將數據和遍歷部分分開，這時就能夠部署IteratorAggregate界面。它規定了一個getIterator()方法，返回一個使用Iterator界面的object。
仍是以上一節的Article類爲例
class Article implements ArrayAccess, IteratorAggregate {
/**
* Defined by IteratorAggregate interface
* Returns an iterator for for this object, for use with foreach
* @return ArrayIterator
*/
function getIterator() {
return new ArrayIterator($this);
}
使用方法以下：
$A = new Article('SPL Rocks','Joe Bloggs', 'PHP');
// Loop (getIterator will be called automatically)
echo 'Looping with foreach:<div>';
foreach ( $A as $field => $value ) {
echo "$field : $value<br>";
}
echo '</div>';
// Get the size of the iterator (see how many properties are left)
echo "Object has ".sizeof($A->getIterator())." elements";
顯示結果以下：
Looping with foreach: title : SPL Rocks author : Joe Bloggs category : PHP Object has 3 elements
六、RecursiveIterator 接口
這個接口用於遍歷多層數據，它繼承了Iterator界面，於是也具備標準的current()、key()、next()、 rewind()和valid()方法。同時，它本身還規定了getChildren()和hasChildren()方法。The getChildren() method must return an object that implements RecursiveIterator.
七、SeekableIterator接口
SeekableIterator界面也是Iterator界面的延伸，除了Iterator的5個方法之外，還規定了seek()方法，參數是元素的位置，返回該元素。若是該位置不存在，則拋出OutOfBoundsException。
下面是一個是實例：
<?php
class PartyMemberIterator implements SeekableIterator
{
public function __construct(PartyMember $member)
{
// Store $member locally for iteration
}
public function seek($index)
{
$this->rewind();
$position = 0;
while ($position < $index && $this->valid()) {
$this->next();
$position++;
}
if (!$this->valid()) {
throw new OutOfBoundsException('Invalid position');
}
}
// Implement current(), key(), next(), rewind()
// and valid() to iterate over data in $member
}
?>
八、Countable 接口
這個接口規定了一個count()方法，返回結果集的數量。
第三部分 SPL Classes
九、SPL的內置類
SPL除了定義一系列Interfaces之外，還提供一系列的內置類，它們對應不一樣的任務，大大簡化了編程。
查看全部的內置類，可使用下面的代碼：
<?php
// a simple foreach() to traverse the SPL class names
foreach(spl_classes() as $key=>$value)
{
echo $key.' -> '.$value.'<br />';
}
?>
十、 DirectoryIterator類
這個類用來查看一個目錄中的全部文件和子目錄：
<?php
try{
/*** class create new DirectoryIterator Object ***/
foreach ( new DirectoryIterator('./') as $Item )
{
echo $Item.'<br />';
}
}
/*** if an exception is thrown, catch it here ***/
catch(Exception $e){
echo 'No files Found!<br />';
}
?>
查看文件的詳細信息：
<table>
<?php
foreach(new DirectoryIterator('./' ) as $file )
{
if( $file->getFilename() == 'foo.txt' )
{
echo '<tr><td>getFilename()</td><td> '; var_dump($file->getFilename()); echo '</td></tr>';
echo '<tr><td>getBasename()</td><td> '; var_dump($file->getBasename()); echo '</td></tr>';
echo '<tr><td>isDot()</td><td> '; var_dump($file->isDot()); echo '</td></tr>';
echo '<tr><td>__toString()</td><td> '; var_dump($file->__toString()); echo '</td></tr>';
echo '<tr><td>getPath()</td><td> '; var_dump($file->getPath()); echo '</td></tr>';
echo '<tr><td>getPathname()</td><td> '; var_dump($file->getPathname()); echo '</td></tr>';
echo '<tr><td>getPerms()</td><td> '; var_dump($file->getPerms()); echo '</td></tr>';
echo '<tr><td>getInode()</td><td> '; var_dump($file->getInode()); echo '</td></tr>';
echo '<tr><td>getSize()</td><td> '; var_dump($file->getSize()); echo '</td></tr>';
echo '<tr><td>getOwner()</td><td> '; var_dump($file->getOwner()); echo '</td></tr>';
echo '<tr><td>$file->getGroup()</td><td> '; var_dump($file->getGroup()); echo '</td></tr>';
echo '<tr><td>getATime()</td><td> '; var_dump($file->getATime()); echo '</td></tr>';
echo '<tr><td>getMTime()</td><td> '; var_dump($file->getMTime()); echo '</td></tr>';
echo '<tr><td>getCTime()</td><td> '; var_dump($file->getCTime()); echo '</td></tr>';
echo '<tr><td>getType()</td><td> '; var_dump($file->getType()); echo '</td></tr>';
echo '<tr><td>isWritable()</td><td> '; var_dump($file->isWritable()); echo '</td></tr>';
echo '<tr><td>isReadable()</td><td> '; var_dump($file->isReadable()); echo '</td></tr>';
echo '<tr><td>isExecutable(</td><td> '; var_dump($file->isExecutable()); echo '</td></tr>';
echo '<tr><td>isFile()</td><td> '; var_dump($file->isFile()); echo '</td></tr>';
echo '<tr><td>isDir()</td><td> '; var_dump($file->isDir()); echo '</td></tr>';
echo '<tr><td>isLink()</td><td> '; var_dump($file->isLink()); echo '</td></tr>';
echo '<tr><td>getFileInfo()</td><td> '; var_dump($file->getFileInfo()); echo '</td></tr>';
echo '<tr><td>getPathInfo()</td><td> '; var_dump($file->getPathInfo()); echo '</td></tr>';
echo '<tr><td>openFile()</td><td> '; var_dump($file->openFile()); echo '</td></tr>';
echo '<tr><td>setFileClass()</td><td> '; var_dump($file->setFileClass()); echo '</td></tr>';
echo '<tr><td>setInfoClass()</td><td> '; var_dump($file->setInfoClass()); echo '</td></tr>';
}
}
?>
</table>
除了foreach循環外，還可使用while循環：
<?php
/*** create a new iterator object ***/
$it = new DirectoryIterator('./');
/*** loop directly over the object ***/
while($it->valid())
{
echo $it->key().' -- '.$it->current().'<br />';
/*** move to the next iteration ***/
$it->next();
}
?>
若是要過濾全部子目錄，能夠在valid()方法中過濾：
<?php
/*** create a new iterator object ***/
$it = new DirectoryIterator('./');
/*** loop directly over the object ***/
while($it->valid())
{
/*** check if value is a directory ***/
if($it->isDir())
{
/*** echo the key and current value ***/
echo $it->key().' -- '.$it->current().'<br />';
}
/*** move to the next iteration ***/
$it->next();
}
?>
十一、ArrayObject類
這個類能夠將Array轉化爲object。
<?php
/*** a simple array ***/
$array = array('koala', 'kangaroo', 'wombat', 'wallaby', 'emu', 'kiwi', 'kookaburra', 'platypus');
/*** create the array object ***/
$arrayObj = new ArrayObject($array);
/*** iterate over the array ***/
for($iterator = $arrayObj->getIterator();
/*** check if valid ***/
$iterator->valid();
/*** move to the next array member ***/
$iterator->next())
{
/*** output the key and current array value ***/
echo $iterator->key() . ' => ' . $iterator->current() . '<br />';
}
?>
增長一個元素：
$arrayObj->append('dingo');
十二、ArrayIterator類
這個類其實是對ArrayObject類的補充，爲後者提供遍歷功能。
示例以下：
<?php
/*** a simple array ***/
$array = array('koala', 'kangaroo', 'wombat', 'wallaby', 'emu', 'kiwi', 'kookaburra', 'platypus');
try {
$object = new ArrayIterator($array);
foreach($object as $key=>$value)
{
echo $key.' => '.$value.'<br />';
}
}
catch (Exception $e)
{
echo $e->getMessage();
}
?>
ArrayIterator類也支持offset類方法和count()方法：
<ul>
<?php
/*** a simple array ***/
$array = array('koala', 'kangaroo', 'wombat', 'wallaby', 'emu', 'kiwi', 'kookaburra', 'platypus');
try {
$object = new ArrayIterator($array);
/*** check for the existence of the offset 2 ***/
if($object->offSetExists(2))
{
/*** set the offset of 2 to a new value ***/
$object->offSetSet(2, 'Goanna');
}
/*** unset the kiwi ***/
foreach($object as $key=>$value)
{
/*** check the value of the key ***/
if($object->offSetGet($key) === 'kiwi')
{
/*** unset the current key ***/
$object->offSetUnset($key);
}
echo '<li>'.$key.' - '.$value.'</li>'."\n";
}
}
catch (Exception $e)
{
echo $e->getMessage();
}
?>
</ul>
1三、RecursiveArrayIterator類和RecursiveIteratorIterator類
ArrayIterator類和ArrayObject類，只支持遍歷一維數組。若是要遍歷多維數組，必須先用RecursiveIteratorIterator生成一個Iterator，而後再對這個Iterator使用RecursiveIteratorIterator。
<?php
$array = array(
array('name'=>'butch', 'sex'=>'m', 'breed'=>'boxer'),
array('name'=>'fido', 'sex'=>'m', 'breed'=>'doberman'),
array('name'=>'girly','sex'=>'f', 'breed'=>'poodle')
);
foreach(new RecursiveIteratorIterator(new RecursiveArrayIterator($array)) as $key=>$value)
{
echo $key.' -- '.$value.'<br />';
}
?>
1四、 FilterIterator類
FilterIterator類能夠對元素進行過濾，只要在accept()方法中設置過濾條件就能夠了。
示例以下：
<?php
/*** a simple array ***/
$animals = array('koala', 'kangaroo', 'wombat', 'wallaby', 'emu', 'NZ'=>'kiwi', 'kookaburra', 'platypus');
class CullingIterator extends FilterIterator{
/*** The filteriterator takes a iterator as param: ***/
public function __construct( Iterator $it ){
parent::__construct( $it );
}
/*** check if key is numeric ***/
function accept(){
return is_numeric($this->key());
}
}/*** end of class ***/
$cull = new CullingIterator(new ArrayIterator($animals));
foreach($cull as $key=>$value)
{
echo $key.' == '.$value.'<br />';
}
?>
下面是另外一個返回質數的例子
<?php
class PrimeFilter extends FilterIterator{
/*** The filteriterator takes a iterator as param: ***/
public function __construct(Iterator $it){
parent::__construct($it);
}
/*** check if current value is prime ***/
function accept(){
if($this->current() % 2 != 1)
{
return false;
}
$d = 3;
$x = sqrt($this->current());
while ($this->current() % $d != 0 && $d < $x)
{
$d += 2;
}
return (($this->current() % $d == 0 && $this->current() != $d) * 1) == 0 ? true : false;
}
}/*** end of class ***/
/*** an array of numbers ***/
$numbers = range(212345,212456);
/*** create a new FilterIterator object ***/
$primes = new primeFilter(new ArrayIterator($numbers));
foreach($primes as $value)
{
echo $value.' is prime.<br />';
}
?>
1五、SimpleXMLIterator類
這個類用來遍歷xml文件。
<?php
/*** a simple xml tree ***/
$xmlstring = <<<XML
<?xml version = "1.0" encoding="UTF-8" standalone="yes"?>
<document>
<animal>
<category id="26">
<species>Phascolarctidae</species>
<type>koala</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="27">
<species>macropod</species>
<type>kangaroo</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="28">
<species>diprotodon</species>
<type>wombat</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="31">
<species>macropod</species>
<type>wallaby</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="21">
<species>dromaius</species>
<type>emu</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="22">
<species>Apteryx</species>
<type>kiwi</type>
<name>Troy</name>
</category>
</animal>
<animal>
<category id="23">
<species>kingfisher</species>
<type>kookaburra</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="48">
<species>monotremes</species>
<type>platypus</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="4">
<species>arachnid</species>
<type>funnel web</type>
<name>Bruce</name>
<legs>8</legs>
</category>
</animal>
</document>
XML;
/*** a new simpleXML iterator object ***/
try {
/*** a new simple xml iterator ***/
$it = new SimpleXMLIterator($xmlstring);
/*** a new limitIterator object ***/
foreach(new RecursiveIteratorIterator($it,1) as $name => $data)
{
echo $name.' -- '.$data.'<br />';
}
}
catch(Exception $e)
{
echo $e->getMessage();
}
?>
new RecursiveIteratorIterator($it,1)表示顯示全部包括父元素在內的子元素。
顯示某一個特定的元素值，能夠這樣寫：
<?php
try {
/*** a new simpleXML iterator object ***/
$sxi = new SimpleXMLIterator($xmlstring);
foreach ( $sxi as $node )
{
foreach($node as $k=>$v)
{
echo $v->species.'<br />';
}
}
}
catch(Exception $e)
{
echo $e->getMessage();
}
?>
相對應的while循環寫法爲
<?php
try {
$sxe = simplexml_load_string($xmlstring, 'SimpleXMLIterator');
for ($sxe->rewind(); $sxe->valid(); $sxe->next())
{
if($sxe->hasChildren())
{
foreach($sxe->getChildren() as $element=>$value)
{
echo $value->species.'<br />';
}
}
}
}
catch(Exception $e)
{
echo $e->getMessage();
}
?>
最方便的寫法，仍是使用xpath：
<?php
try {
/*** a new simpleXML iterator object ***/
$sxi = new SimpleXMLIterator($xmlstring);
/*** set the xpath ***/
$foo = $sxi->xpath('animal/category/species');
/*** iterate over the xpath ***/
foreach ($foo as $k=>$v)
{
echo $v.'<br />';
}
}
catch(Exception $e)
{
echo $e->getMessage();
}
?>
下面的例子，顯示有namespace的狀況：
<?php
/*** a simple xml tree ***/
$xmlstring = <<<XML
<?xml version = "1.0" encoding="UTF-8" standalone="yes"?>
<document xmlns:spec="http://example.org/animal-species">
<animal>
<category id="26">
<species>Phascolarctidae</species>
<spec:name>Speed Hump</spec:name>
<type>koala</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="27">
<species>macropod</species>
<spec:name>Boonga</spec:name>
<type>kangaroo</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="28">
<species>diprotodon</species>
<spec:name>pot holer</spec:name>
<type>wombat</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="31">
<species>macropod</species>
<spec:name>Target</spec:name>
<type>wallaby</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="21">
<species>dromaius</species>
<spec:name>Road Runner</spec:name>
<type>emu</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="22">
<species>Apteryx</species>
<spec:name>Football</spec:name>
<type>kiwi</type>
<name>Troy</name>
</category>
</animal>
<animal>
<category id="23">
<species>kingfisher</species>
<spec:name>snaker</spec:name>
<type>kookaburra</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="48">
<species>monotremes</species>
<spec:name>Swamp Rat</spec:name>
<type>platypus</type>
<name>Bruce</name>
</category>
</animal>
<animal>
<category id="4">
<species>arachnid</species>
<spec:name>Killer</spec:name>
<type>funnel web</type>
<name>Bruce</name>
<legs>8</legs>
</category>
</animal>
</document>
XML;
/*** a new simpleXML iterator object ***/
try {
/*** a new simpleXML iterator object ***/
$sxi = new SimpleXMLIterator($xmlstring);
$sxi-> registerXPathNamespace('spec', 'http://www.exampe.org/species-title');
/*** set the xpath ***/
$result = $sxi->xpath('//spec:name');
/*** get all declared namespaces ***/
foreach($sxi->getDocNamespaces('animal') as $ns)
{
echo $ns.'<br />';
}
/*** iterate over the xpath ***/
foreach ($result as $k=>$v)
{
echo $v.'<br />';
}
}
catch(Exception $e)
{
echo $e->getMessage();
}
?>
增長一個節點：
<?php
$xmlstring = <<<XML
<?xml version = "1.0" encoding="UTF-8" standalone="yes"?>
<document>
<animal>koala</animal>
<animal>kangaroo</animal>
<animal>wombat</animal>
<animal>wallaby</animal>
<animal>emu</animal>
<animal>kiwi</animal>
<animal>kookaburra</animal>
<animal>platypus</animal>
<animal>funnel web</animal>
</document>
XML;
try {
/*** a new simpleXML iterator object ***/
$sxi = new SimpleXMLIterator($xmlstring);
/*** add a child ***/
$sxi->addChild('animal', 'Tiger');
/*** a new simpleXML iterator object ***/
$new = new SimpleXmlIterator($sxi->saveXML());
/*** iterate over the new tree ***/
foreach($new as $val)
{
echo $val.'<br />';
}
}
catch(Exception $e)
{
echo $e->getMessage();
}
?>
增長屬性：
<?php
$xmlstring =<<<XML
<?xml version = "1.0" encoding="UTF-8" standalone="yes"?>
<document>
<animal>koala</animal>
<animal>kangaroo</animal>
<animal>wombat</animal>
<animal>wallaby</animal>
<animal>emu</animal>
<animal>kiwi</animal>
<animal>kookaburra</animal>
<animal>platypus</animal>
<animal>funnel web</animal>
</document>
XML;
try {
/*** a new simpleXML iterator object ***/
$sxi = new SimpleXMLIterator($xmlstring);
/*** add an attribute with a namespace ***/
$sxi->addAttribute('id:att1', 'good things', 'urn::test-foo');
/*** add an attribute without a namespace ***/
$sxi->addAttribute('att2', 'no-ns');
echo htmlentities($sxi->saveXML());
}
catch(Exception $e)
{
echo $e->getMessage();
}
?>
1六、CachingIterator類
這個類有一個hasNext()方法，用來判斷是否還有下一個元素。
示例以下：
<?php
/*** a simple array ***/
$array = array('koala', 'kangaroo', 'wombat', 'wallaby', 'emu', 'kiwi', 'kookaburra', 'platypus');
try {
/*** create a new object ***/
$object = new CachingIterator(new ArrayIterator($array));
foreach($object as $value)
{
echo $value;
if($object->hasNext())
{
echo ',';
}
}
}
catch (Exception $e)
{
echo $e->getMessage();
}
?>
1七、LimitIterator類
這個類用來限定返回結果集的數量和位置，必須提供offset和limit兩個參數，與SQL命令中limit語句相似。
示例以下：
<?php
/*** the offset value ***/
$offset = 3;
/*** the limit of records to show ***/
$limit = 2;
$array = array('koala', 'kangaroo', 'wombat', 'wallaby', 'emu', 'kiwi', 'kookaburra', 'platypus');
$it = new LimitIterator(new ArrayIterator($array), $offset, $limit);
foreach($it as $k=>$v)
{
echo $it->getPosition().'<br />';
}
?>
另外一個例子是：
<?php
/*** a simple array ***/
$array = array('koala', 'kangaroo', 'wombat', 'wallaby', 'emu', 'kiwi', 'kookaburra', 'platypus');
$it = new LimitIterator(new ArrayIterator($array));
try
{
$it->seek(5);
echo $it->current();
}
catch(OutOfBoundsException $e)
{
echo $e->getMessage() . "<br />";
}
?>
1八、SplFileObject類
這個類用來對文本文件進行遍歷。
示例以下：
<?php
try{
// iterate directly over the object
foreach( new SplFileObject("/usr/local/apache/logs/access_log") as $line)
// and echo each line of the file
echo $line.'<br />';
}
catch (Exception $e)
{
echo $e->getMessage();
}
?>
返回文本文件的第三行，能夠這樣寫：
<?php
try{
$file = new SplFileObject("/usr/local/apache/logs/access_log");
$file->seek(3);
echo $file->current();
}
catch (Exception $e)
{
echo $e->getMessage();
}
?>
[參考文獻]
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