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"; }
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Will output:
var1 => value 1 var2 => value 2 var3 => value 3
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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"; }
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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:
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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>
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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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