note 116572 added to language.generators.syntax

You can use generators to do lazy loading of lists. You only compute the items that are actually used. However, when you want to load more items, how to cache the ones already loaded? Here is how to do cached lazy loading with a generator: <?php class Foobar { public function loader() { foreach(range(0,10) as $i) { usleep(200000); yield $i; } } public function getItems() { static $loader = null, $cache = []; $loader = $loader ?: $this->loadItems(); foreach($cache as $item) yield $item; while( $loader->valid() ) { $cache[] = $current = $loader->current(); $loader->next(); yield $current; } } } $f = new Foobar; # First print "First\n"; foreach($f->getItems() as $i) { print $i . "\n"; if( $i == 5 ) { break; } } # Second (items 1-5 are cached, 6-10 are loaded) print "Second\n"; foreach($f->getItems() as $i) { print $i . "\n"; } # Third (all items are cached and returned instantly) print "Third\n"; foreach($f->getItems() as $i) { print $i . "\n"; } ---- Server IP: 72.52.91.14 Probable Submitter: 2001:980:d784:1:f917:a27b:d077:2ac7 ---- Manual Page -- http://php.net/manual/en/language.generators.syntax.php Edit -- https://master.php.net/note/edit/116572 Del: integrated -- https://master.php.net/note/delete/116572/integrated Del: useless -- https://master.php.net/note/delete/116572/useless Del: bad code -- https://master.php.net/note/delete/116572/bad+code Del: spam -- https://master.php.net/note/delete/116572/spam Del: non-english -- https://master.php.net/note/delete/116572/non-english Del: in docs -- https://master.php.net/note/delete/116572/in+docs Del: other reasons-- https://master.php.net/note/delete/116572 Reject -- https://master.php.net/note/reject/116572 Search -- https://master.php.net/manage/user-notes.php