PHP 手冊
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# Object Iteration

PHP 5 provides a way for objects to be defined so it is possible to iterate through a list of items, with, for example a the 節 called foreach 在 11 章 statement. By default, all public properties will be used for the iteration.

示範 14-14.Simple Object Iteration

`<?php class MyClass { public $var1 = 'value 1'; public $var2 = 'value 2'; public $var3 = 'value 3'; protected $protected = 'protected'; private $private = 'private'; } $class = new MyClass(); foreach($class as $key => $value) { print "$key => $value\n"; }`

Will output:

`var1 => value 1 var2 => value 2 var3 => value 3`

As the output shows, the the 節 called foreach 在 11 章 iterated through each public variable that is defined. To take it a step further you can implement one of PHP 5's internal the 節 called Object Interfaces named Iterator. This allows the object to decide what and how the object will be iterated.

示範 14-15.Object Iteration implenting Iterator

`<?php
class MyIterator implements Iterator {
private $var = array();
public function __construct($array) {
if (is_array($array) ) {
$this->var = $array;
}
}
public function rewind() {
echo "rewinding\n";
reset($this->var);
}
public function current() {
$var = current($this->var);
echo "current: $var\n";
return $var;
}
public function key() {
$var = key($this->var);
echo "key: $var\n";
return $var;
}
public function next() {
$var = next($this->var);
echo "next: $var\n";
return $var;
}
public function valid() {
$var = $this->current() !== false;
echo "valid: {$var}\n";
return $var;
}
}
$values = array(1,2,3);
$it = new MyIterator($values);
foreach ($it as $a => $b) {
print "$a: $b\n";
}`

Will output:

`rewinding current: 1 valid: 1 current: 1 key: 0 0: 1 next: 2 current: 2 valid: 1 current: 2 key: 1 1: 2 next: 3 current: 3 valid: 1 current: 3 key: 2 2: 3 next: current: valid:`

You can also define your class so that it doesn't have to define all the Iterator functions by simply implementing the PHP 5 IteratorAggregate interface.

示範 14-16.Object Iteration implenting IteratorAggregate

`<?php
class MyCollection implements IteratorAggregate {
private $items = array();
private $count = 0;
/* Required definition of interface IteratorAggregate */
public function getIterator() {
return new MyIterator($this->items);
}
public function add($value) {
$this->items[$this->count++] = $value;
}
}
$coll = new MyCollection();
$coll->add('value 1');
$coll->add('value 2');
$coll->add('value 3');
foreach ($coll as $key => $val) {
echo "key/value: [$key -> $val]\n\n";
}
?>
</pre>`

Will output:

`rewinding current: value 1 valid: 1 current: value 1 key: 0 key/value: [0 -> value 1] next: value 2 current: value 2 valid: 1 current: value 2 key: 1 key/value: [1 -> value 2] next: value 3 current: value 3 valid: 1 current: value 3 key: 2 key/value: [2 -> value 3] next: current: valid:`

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