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 Abschnitt namens foreach in Kapitel 15 statement. By default, all
public properties will be used for the iteration.
Beispiel 18-14. 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 Abschnitt namens foreach in Kapitel 15
iterated through each public variable that is defined. To take it
a step further you can implement one of PHP 5's
internal Abschnitt namens Object Interfaces named
Iterator. This allows the object to decide what
and how the object will be iterated.
Beispiel 18-15. 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.
Beispiel 18-16. 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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