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 foreach statement. By default, all visible properties will be used for the iteration.
Example #1 Simple Object Iteration
<?php
class?MyClass
{
????public?$var1?=?'value?1';
????public?$var2?=?'value?2';
????public?$var3?=?'value?3';
????protected?$protected?=?'protected?var';
????private???$private???=?'private?var';
????function?iterateVisible()?{
???????echo?"MyClass::iterateVisible:\n";
???????foreach?($this?as?$key?=>?$value)?{
???????????print?"$key?=>?$value\n";
???????}
????}
}
$class?=?new?MyClass();
foreach($class?as?$key?=>?$value)?{
????print?"$key?=>?$value\n";
}
echo?"\n";
$class->iterateVisible();
?>The above example will output:
var1 => value 1
var2 => value 2
var3 => value 3
MyClass::iterateVisible:
var1 => value 1
var2 => value 2
var3 => value 3
protected => protected var
private => private varAs the output shows, the foreach iterated through all of the visible properties that could be accessed.
To take it a step further, the Iterator interface may be implemented. This allows the object to dictate how it will be iterated and what values will be available on each iteration.
Example #2 Object Iteration implementing Iterator
<?php
class?MyIterator?implements?Iterator
{
????private?$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?$var;
????}
??
????public?function?valid()
????{
????????$key?=?key($this->var);
????????$var?=?($key?!==?NULL?&&?$key?!==?FALSE);
????????echo?"valid:?$var\n";
????????return?$var;
????}
}
$values?=?array(1,2,3);
$it?=?new?MyIterator($values);
foreach?($it?as?$a?=>?$b)?{
????print?"$a:?$b\n";
}
?>The above example will output:
rewinding
valid: 1
current: 1
key: 0
0: 1
next: 2
valid: 1
current: 2
key: 1
1: 2
next: 3
valid: 1
current: 3
key: 2
2: 3
next:
valid: The IteratorAggregate interface can be used as an alternative to implementing all of the Iterator methods. IteratorAggregate only requires the implementation of a single method, IteratorAggregate::getIterator(), which should return an instance of a class implementing Iterator.
Example #3 Object Iteration implementing IteratorAggregate
<?php
class?MyCollection?implements?IteratorAggregate
{
????private?$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";
}
?>The above example 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:Note: For more examples of iterators, see the SPL Extension. Note: Users of PHP 5.5 and later may also want to investigate generators, which provide an alternative way of defining iterators.
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Magic Methods →
? 1997–2017 The PHP Documentation GroupLicensed under the Creative Commons Attribution License v3.0 or later.
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