• Iterators
• Collections in PHP
• Generators
• PHP is fun

Iterators

function doStuff(array $things) {
    foreach ($things as $thing) {
        /* ... */
    }
}
					

function doStuff(Iterator $things) {
    foreach ($things as $thing) {
        /* ... */
    }
}
					

Find the cat

• Directory with .txt files
• One contains ~=[,,_,,]:3

function findFileWithNyanCat(string $path): ?string {
    foreach (glob($path . '*.txt') as $file) {
        $fileContent = file_get_contents($file);

        if (in_string('~=[,,_,,]:3', $fileContent)) {
            return $fileContent;
        }
    }
    return null;
}
					

function getContentsOfTextFiles($path): array {
    // glob and file_get_contents
}

function findTextWithNyanCat(array $texts): ?string {
    foreach ($texts as $text) {
        if (in_string('~=[,,_,,]:3', $text)) {
            return $text;
        }
    }
    return null;
}

findTextWithNyanCat(getContentsOfTextFiles($path));
					

class TextFileIterator implements Iterator {
    /* ... */
    public function current() {
        // return file_get_contents
    }
    /* ... */
}
					

function findTextWithNyanCat(Iterator $texts): ?string {
    foreach ($texts as $text) {
        if (in_string('~=[,,_,,]:3', $text)) { /*...*/ }
    }
    return null;
}

findTextWithNyanCat(new TextFileIterator($path));
					

findTextWithNyanCat(new DatabaseIterator(/*...*/));
findTextWithNyanCat(new ArrayIterator(['test text', '~=[,,_,,]:3']));
					

Generators

function newNyanGenerator(): Generator {
    yield '~=[,,_,,]:3';
    yield 'Nyan!';
}

$generator = newNyanGenerator();

foreach ($generator as $text) {
    echo $text . ' ';
}

// ~=[,,_,,]:3 Nyan!
					

• new LimitIterator(Iterator $i)
• new CachingIterator(Iterator $i)

IteratorAggregate + Generator = <3

function newNyanGenerator(): Generator {
    yield '~=[,,_,,]:3';
    yield 'Nyan!';
}

$generator = newNyanGenerator();

foreach ($generator as $text) {
    echo $text;
}
foreach ($generator as $text) {
    echo $text; // BOOM!
}
					

interface IteratorAggregate extends Traversable {
    public function getIterator(): Traversable;
}
					

class NyanNyan implements IteratorAggregate {
    public function getIterator(): Traversable {
        yield '~=[,,_,,]:3';
        yield 'Nyan!';
    }
}

$traversable = new NyanNyan();

foreach ($traversable as $text) {
    echo $text;
}
foreach ($traversable as $text) {
    echo $text; // works fine
}
					

Real world example

private function getMailTemplatesOnDisk(array $mailTemplatePaths): array {
    $mailTemplatesOnDisk = [];

    foreach ($mailTemplatePaths as $path) {
        $mailFilesInFolder = glob($path . '/Mail_*');
        array_walk($mailFilesInFolder, function(&$filename) {
            $filename = basename($filename);
        });
        $mailTemplatesOnDisk = array_merge($mailTemplatesOnDisk, $mailFilesInFolder);
    }

    return $mailTemplatesOnDisk;
}
					

class MailTemplateFilenameTraversable implements \IteratorAggregate {
    public function __construct(array $mailTemplatePaths) {
        $this->mailTemplatePaths = $mailTemplatePaths;
    }

    public function getIterator() {
        foreach ($this->mailTemplatePaths as $path) {
            foreach (glob( $path . '/Mail_*') as $fileName) {
                yield basename($fileName);
            }
        }
    }
}
					

function doStuff(iterable $things) {
    foreach ($things as $thing) {
        /* ... */
    }
}
					

function doStuff(iterable $things) {
    foreach (array_chunk($things, 2) as $twoThings) {
        /* ... */
    }
}
					

function iterable_to_array(iterable $iterable): array {
    if (is_array($iterable)) {
        return $iterable;
    }
    return iterator_to_array($iterable);
}
					

iterable → Iterator

function iterable_to_iterator(iterable $iterable): Iterator {
    if ($iterable instanceof Iterator) {
        return $iterable;
    }
    if (is_array($iterable)) {
        return new ArrayIterator($iterable);
    }

    // TODO: IteratorAggregate case
}
					

    return new IteratorIterator($iterable);
					

interface IteratorAggregate extends Traversable {
    public function getIterator();
}
					

    return new \WMDE\TraversableIterator\TraversableIterator($iterable);
						

Cattribution

• "First slide cat" by Pacto Visual
• "Overview cat" by Susann Mielke
• "Iterators cat" by Josh Couch
• "Find the cat" by Stephan Henning
• "Nyan search cats" by Raul Varzar
• "Collection hierarchy cat" by Borna Bevanda
• "Generators cat" by Lodewijk Hertog
• "IteratorAggregate+Generator cat" by Paul Hanaoka
• "Rewindable Generator cat" by Ludemeula Fernandes
• "Real world example cat" by Daria Nepriakhina
• "Mail templates cat" by Jason Blackeye
• "Generators also can cat" by Taylor Grote
• "PHPUnit yield cat" by James Sutton
• "PHP is fun cat" by Mikhail Vasilyev
• "Questions cat" by "Kessa"
• "Attribution cats" by Florencia Lewis, CC BY 2.0
• These slides by Jeroen De Dauw

Questions?