note 107533 added to control-structures.foreach

You can even iterate through "dynamic" arrays that do not physically exist, but are objects that implement Iterator interface. They don't need to be stored in memory when foreach starts. Consider the array that contains some values (I called it $allValues in the example below) and we want to have only some of them (eg. the ones that are dividable by 2). I create an object that would serve as dynamic array, that means it would "dynamically update" its values together with $allValues. The main advantage is that I store only one array, and it's the only array I serialize. An object of MyIter class will not contain any values itself: <?php class MyIter implements Iterator { // you can implement ArrayAccess and Countable interfaces too, this will make class MyIter behave like a "real" array private $position = 0; // an internal position of the current element // please note that $position has nothing common with $allValues! private function getTable(){ // prepare a temporary "static" table of all objects in the class global $allValues; $result=array(); // temporary variable foreach($allValues as $obj){ if($obj % 2 == 0) // check if the value is even $result[]=$obj; // if yes, I want it } return $result; } // the all below declared methods are public and belong to the Iterator interface function rewind() { // a method to start iterating $this->position = 0; // just move to the beginning } function current() { // retrieves the current element $table=$this->getTable(); // let us prepare a table return $table[$this->position]; // and return the current element } function key() { // retrieves the current element's key return $this->position; // this is used by foreach(... as $key=>$value), not important here } function next() { // move to next element ++$this->position; } function valid() { // check if the current element is valid (ie. if it exists) return array_key_exists($this->position, $this->getTable()); } } // end of class // now prepare the array of 12 elements $allValues=array(0,1,2,3,4,5,6,7,8,9,10,11); //we would like to have a dynamic array of all even values $iterator=new MyIter(); foreach($iterator as $value){ echo $value."<br />"; } ?> This will result in: 0 2 4 6 8 10 (You may also like to see what var_dump($iterator) produces). Another great advantage is that you can modify the main table "on-the-fly" and it has its impact. Let us modify the last foreach loop: <?php // ...all above shall stay as it was foreach($iterator as $value){ echo $value."<br />"; if($value==6){ $allValues=array(2,3); echo "I modified source array!<br />"; } } ?> This produces now: 0 2 4 6 I modified source array! However, if you feel it is rather a catastrophic disadvantage (maybe for example, it shows the values 0, 4, and 6 which were removed when we reached 6), and wish to have a "static" array that will iterate even in modified objects, just call getTable() in rewind() method and save it in temporary (private perhaps) field. In my example getTable() is called every iteration, and it calls another foreach through $allValues, which together might be time-consuming. Consider what you need. ---- Server IP: 82.177.164.100 Probable Submitter: 89.75.186.180 ---- Manual Page -- http://www.php.net/manual/en/control-structures.foreach.php Edit -- https://master.php.net/note/edit/107533 Del: integrated -- https://master.php.net/note/delete/107533/integrated Del: useless -- https://master.php.net/note/delete/107533/useless Del: bad code -- https://master.php.net/note/delete/107533/bad+code Del: spam -- https://master.php.net/note/delete/107533/spam Del: non-english -- https://master.php.net/note/delete/107533/non-english Del: in docs -- https://master.php.net/note/delete/107533/in+docs Del: other reasons-- https://master.php.net/note/delete/107533 Reject -- https://master.php.net/note/reject/107533 Search -- https://master.php.net/manage/user-notes.php