Generated Power: PHP 5.5 Generators

Generated Power

PHP 5.5 – Generators

Who am I?

Mark BakerDesign and Development ManagerInnovEd (Innovative Solutions for Education) Learning Ltd

Coordinator and Developer of:Open Source PHPOffice library

PHPExcel, PHPWord,PHPPowerPoint, PHPProject, PHPVisioMinor contributor to PHP coreOther small open source libraries available on github

@Mark_Baker

https://github.com/MarkBaker

http://uk.linkedin.com/pub/mark-baker/b/572/171


• Introduced in PHP 5.5• Iterable Objects• Can return a series of values, one at a time• Can accept values when sent to the generator• Maintain state between iterations• Similar to enumerators in Ruby


• Don’t • Add anything to PHP that couldn’t be done before

• Do• Allow you to perform iterative operations without an array to iterate• Potentially reduce memory use• Potentially faster than iterating over an array• Potentially cleaner and shorter code


• Automatically created when PHP identifies a function or method containing the “yield” keyword

function myGenerator() { yield 1; }

$generator = myGenerator(); var_dump($generator);

object(Generator)#1 (0) { }


• Implemented as an Object

final class Generator implements Iterator { void rewind(); bool valid(); mixed current(); mixed key(); void next(); mixed send(mixed $value);}

•Can’t be extended


function xrange($lower, $upper) { for ($i = $lower; $i <= $upper; ++$i) { yield $i; } }

$rangeGenerator = xrange(0,10);

while ($rangeGenerator->valid()) { $key = $rangeGenerator->key(); $value = $rangeGenerator->current(); echo $key , ' -> ' , $value, PHP_EOL; $rangeGenerator->next(); }


function xrange($lower, $upper) { for ($i = $lower; $i <= $upper; ++$i) { yield $i; } }

foreach (xrange(0,10) as $key => $value) { echo $key , ' -> ' , $value, PHP_EOL; }


foreach (range(0,65535) as $i => $value) { echo $i , ' -> ' , $value, PHP_EOL;}

function xrange($lower, $upper) { for ($i = $lower; $i <= $upper; ++$i) { yield $i; }}

foreach (xrange(0, 65535) as $i => $value) { echo $i , ' -> ' , $value, PHP_EOL;}

for($i = 0; $i <= 65535; ++$i) { echo $i , ' -> ' , $value, PHP_EOL;}

Time: 0.0183 s

Current Memory: 123.44 k

Peak Memory: 5500.11 k

Time: 0.0135 s



Time: 0.0042 s




function fibonacci($count) { $prev = 0; $current = 1;

for ($i = 0; $i < $count; ++$i) { yield $prev; $current = $prev + $current; $prev = $current - $prev; }}

foreach (fibonacci(15) as $i => $value) { echo $i , ' -> ' , $value, PHP_EOL;}

0 -> 0

1 -> 1

2 -> 1

3 -> 2

4 -> 3

5 -> 5

6 -> 8

7 -> 13

8 -> 21

9 -> 34

10 -> 55

11 -> 89

12 -> 144

13 -> 233

14 -> 377

15 -> 610


function xlColumnRange($lower, $upper) {

++$upper;

for ($i = $lower; $i != $upper; ++$i) {

yield $i;

}

}

foreach (xlColumnRange('A', 'CQ') as $i =>

$value) {

printf('%3d -> %2s', $i, $value);

echo (($i > 0) && ($i+1 % 5 == 0)) ?

PHP_EOL :

"\t";

}

0 -> A 1 -> B 2 -> C 3 -> D 4 -> E

5 -> F 6 -> G 7 -> H 8 -> I 9 -> J

10 -> K 11 -> L 12 -> M 13 -> N 14 -> O

15 -> P 16 -> Q 17 -> R 18 -> S 19 -> T

20 -> U 21 -> V 22 -> W 23 -> X 24 -> Y

25 -> Z 26 -> AA 27 -> AB 28 -> AC 29 -> AD

30 -> AE 31 -> AF 32 -> AG 33 -> AH 34 -> AI

35 -> AJ 36 -> AK 37 -> AL 38 -> AM 39 -> AN

40 -> AO 41 -> AP 42 -> AQ 43 -> AR 44 -> AS

45 -> AT 46 -> AU 47 -> AV 48 -> AW 49 -> AX

50 -> AY 51 -> AZ 52 -> BA 53 -> BB 54 -> BC

55 -> BD 56 -> BE 57 -> BF 58 -> BG 59 -> BH

60 -> BI 61 -> BJ 62 -> BK 63 -> BL 64 -> BM

65 -> BN 66 -> BO 67 -> BP 68 -> BQ 69 -> BR

70 -> BS 71 -> BT 72 -> BU 73 -> BV 74 -> BW

75 -> BX 76 -> BY 77 -> BZ 78 -> CA 79 -> CB

80 -> CC 81 -> CD 82 -> CE 83 -> CF 84 -> CG

85 -> CH 86 -> CI 87 -> CJ 88 -> CK 89 -> CL

90 -> CM 91 -> CN 92 -> CO 93 -> CP 94 -> CQ


$isEven = function ($value) {

return !($value & 1);

};

$isOdd = function ($value) {

return $value & 1;

};

function xFilter(callable $callback, array $args=array()) {

foreach($args as $arg)

if (call_user_func($callback, $arg))

yield $arg;

}

$data = range(1,10);

echo 'xFilter for Odd Numbers', PHP_EOL;

foreach(xFilter($isOdd, $data) as $i)

echo('num is: '.$i.PHP_EOL);

echo 'xFilter for Even Numbers', PHP_EOL;

foreach(xFilter($isEven, $data) as $i)

echo('num is: '.$i.PHP_EOL);

xFilter for Odd Numbers

num is: 1

num is: 3

num is: 5

num is: 7

num is: 9

xFilter for Even Numbers

num is: 2

num is: 4

num is: 6

num is: 8

num is: 10

PHP 5.5 – Generators// Endpoint is Brighton

$endPoint = new \DistanceCalculator(

50.8429,

0.1313

);

function retrieveCityData(\DistanceCalculator $endPoint) {

$file = new \SplFileObject("cities.csv");

$file->setFlags(

SplFileObject::DROP_NEW_LINE |

SplFileObject::SKIP_EMPTY

);

while (!$file->eof()) {

$cityData = $file->fgetcsv();

if ($cityData !== NULL) {

$city = new \StdClass;

$city->name = $cityData[0];

$city->latitude = $cityData[1];

$city->longitude = $cityData[2];

$city->distance = $endPoint->calculateDistance($city);

yield $city;

}

}

}

foreach (retrieveCityData($endPoint) as $city) {

echo $city->name, ' is ', sprintf('%.2f', $city->distance), ' miles from Brighton', PHP_EOL;

}


• Can return both a value and a “pseudo” key• By default• The key is an integer value• Starting with 0 for the first iteration• Incrementing by 1 each iteration

• Accessed from foreach() as:foreach(generator() as $key => $value) {}

• or using$key = $generatorObject->key();


• Default key behaviour can be changed• Syntax is:

yield $key => $value;

• Unlike array keys:• “Pseudo” keys can be any PHP datatype• “Pseudo” key values can be duplicated


function xrange($lower, $upper) { $k = 0; for ($i = $lower; $i <= $upper; ++$i) { yield ++$k => $i; }}

foreach (xrange(0,10) as $i => $value) { echo $i , ' -> ' , $value, PHP_EOL;}


function duplicateKeys($lower, $upper) {

for ($i = $lower; $i <= $upper; ++$i) {

yield (($i-1) % 3) + 1 => $i;

}

}

foreach (duplicateKeys(1,15) as $i => $value)

{

echo $i , ' -> ' , $value, PHP_EOL;

}

1 -> 1

2 -> 2

3 -> 3

1 -> 4

2 -> 5

3 -> 6

1 -> 7

2 -> 8

3 -> 9

1 -> 10

2 -> 11

3 -> 12

1 -> 13

2 -> 14

3 -> 15


function duplicateKeys($string) {

$string = strtolower($string);

$length = strlen($string);

for ($i = 0; $i < $length; ++$i) {

yield

strpos($string, $string[$i]) =>

$string[$i];

}

}

foreach (duplicateKeys('badass') as $i => $value) {

echo $i , ' -> ' , $value, PHP_EOL;

}

0 -> b

1 -> a

2 -> d

1 -> a

4 -> s

4 -> s


function floatKeys($lower, $upper) {

for ($i = $lower; $i <= $upper; ++$i) {

yield ($i / 5) => $i;

}

}

foreach (floatKeys(1,16) as $i => $value) {

printf(

'%0.2f -> %2d' . PHP_EOL,

$i,

$value

);

}

0.20 -> 1

0.40 -> 2

0.60 -> 3

0.80 -> 4

1.00 -> 5

1.20 -> 6

1.40 -> 7

1.60 -> 8

1.80 -> 9

2.00 -> 10

2.20 -> 11

2.40 -> 12

2.60 -> 13

2.80 -> 14

3.00 -> 15

3.20 -> 16

PHP 5.5 – Generators// Endpoint is Brighton

$endPoint = new \DistanceCalculator(

50.8429,

0.1313

);

function retrieveCityData(\DistanceCalculator $endPoint) {

$file = new \SplFileObject("cities.csv");

$file->setFlags(

SplFileObject::DROP_NEW_LINE |

SplFileObject::SKIP_EMPTY

);


$cityData = $file->fgetcsv();

if ($cityData !== NULL) {

$city = new \StdClass;

$city->name = $cityData[0];

$city->latitude = $cityData[1];

$city->longitude = $cityData[2];

yield $city => $endPoint->calculateDistance($city);

}

}

}

foreach (retrieveCityData($endPoint) as $city => $distance) {

echo $city->name, ' is ', sprintf('%.2f', $distance), ' miles from Brighton', PHP_EOL;

}


• Data can be passed to the generator• Called a “coroutine” when used in this way• Syntax is:

$value = yield;

• Calling script uses the “send” method:$generatorObject->send($value);


$data = array(

'London',

'New York',

'Paris',

'Munich',

);

function generatorSend() {

while (true) {

$cityName = yield;

echo $cityName, PHP_EOL;

}

}

$generatorObject = generatorSend();

foreach($data as $value) {

$generatorObject->send($value);

}

LondonNew YorkParisMunich

PHP 5.5 – Generators$logFileName = __DIR__ . '/error.log';

function logger($logFileName) {

$f = fopen($logFileName, 'a');

while ($logentry = yield) {

fwrite(

$f,

(new DateTime())->format('Y-m-d H:i:s ') .

$logentry .

PHP_EOL

);

}

}

$logger = logger($logFileName);

for($i = 0; $i < 12; ++$i) {

$logger->send('Message #' . $i );

}


• It is possible to combine a Generator to both send and accept data


function generatorSend($limit) {

for ($i = 1; $i <= $limit; ++$i) {

yield $i => pow($i, $i);

$continue = yield;

if (!$continue)

break;

}

}

$generatorObject = generatorSend(100);

$carryOnRegardless = true;

while ($generatorObject->valid()) {

$key = $generatorObject->key();

$value = $generatorObject->current();

if ($key >= 10)

$carryOnRegardless = false;

$generatorObject->next();

$generatorObject->send($carryOnRegardless);

echo $key, ' -> ', $value, PHP_EOL;

}

1 -> 1

2 -> 4

3 -> 27

4 -> 256

5 -> 3125

6 -> 46656

7 -> 823543

8 -> 16777216

9 -> 387420489

10 -> 10000000000

PHP 5.5 – Generators (Gotcha)


for ($i = 1; $i <= $limit; ++$i) {

yield pow($i, $i);

$continue = yield;

if (!$continue)

break;

}

}



while ($generatorObject->valid()) {



if ($key >= 10)


$generatorObject->next();



}

0 -> 1

2 -> 4

4 -> 27

6 -> 256

8 -> 3125

10 -> 46656



for ($i = 1; $i <= $limit; ++$i) {

$continue = (yield pow($i, $i));

if (!$continue)

break;

}

}



while($generatorObject->valid()) {




if ($key >= 10)



}

0 -> 1

1 -> 4

2 -> 27

3 -> 256

4 -> 3125

5 -> 46656

6 -> 823543

7 -> 16777216

8 -> 387420489

9 -> 10000000000

PHP 5.5 – Generatorsfunction bingo($card) {

$card = array_flip($card);

while (!empty($card)) {

$number = yield;

echo 'Checking card';

if (isset($card[$number])) {

echo ' - Match';

unset($card[$number]);

}

if (empty($card)) {

echo ' *** HOUSE ***';

} else {

echo ' - ', count($card),

' number',

(count($card) == 1 ? '' : 's'),

' left';

}

yield empty($card);

}

}

PHP 5.5 – Generators$players = array();

foreach($playerNames as $playerName) {

shuffle($numbers);

$card = array_slice($numbers,0,$cardSize);

$player = new \StdClass();

$player->name = $playerName;

$player->checknumbers = bingo($card);

$players[] = $player;

}

$houseCalled = false;

while (!$houseCalled && !empty($numbers)) {

$number = array_pop($numbers);

echo PHP_EOL, 'Caller Draws ', $number, PHP_EOL;

foreach($players as $player) {

echo $player->name, ': ';

$player->checknumbers->send($number);

$houseCalled = $player->checknumbers->current();

if ($houseCalled) {

echo PHP_EOL, PHP_EOL, $player->name, ' WINS';

break;

}

$player->checknumbers->next();

echo PHP_EOL;

}

}

Matthew has 3,8,11

Mark has 6,7,11

Luke has 3,9,12

John has 3,7,12

Brian has 1,7,9

Caller Draws 9

Matthew: Checking card - 3 numbers left

Mark: Checking card - 3 numbers left

Luke: Checking card - Match - 2 numbers left

John: Checking card - 3 numbers left

Brian: Checking card - Match - 2 numbers left

Caller Draws 1



Luke: Checking card - 2 numbers left


Brian: Checking card - Match - 1 number left

Caller Draws 4





Brian: Checking card - 1 number left

Caller Draws 7


Mark: Checking card - Match - 2 numbers left


John: Checking card - Match - 2 numbers left

Brian: Checking card - Match *** HOUSE ***

Brian WINS

PHP 5.5 – Generatorspublic function search(QuadTreeBoundingBox $boundary) {

$results = array();

if ($this->boundingBox->encompasses($boundary) ||

$this->boundingBox->intersects($boundary)) {

// Test each point that falls within the current QuadTree node

foreach($this->points as $point) {

// Test each point stored in this QuadTree node in turn,

// passing back to the caller if it falls within the bounding box

if ($boundary->containsPoint($point)) {

yield $point;

}

}

// If we have child QuadTree nodes....

if (isset($this->northWest)) {

// ... search each child node in turn, merging with any existing results

foreach($this->northWest->search($boundary) as $result)

yield $result;

foreach($this->northEast->search($boundary) as $result)

yield $result;

foreach($this->southWest->search($boundary) as $result)

yield $result;

foreach($this->southEast->search($boundary) as $result)

yield $result;

}

}

}

PHP 5.5 – Generators$files = glob('server*.log');

$domain = 'innovedtest.co.uk';

$pregDomain = '/' . preg_quote($domain) . '/';

function searchLogData($fileName, $searchDomain) {

$file = new \SplFileObject($fileName);


$logData = $file->fgets();

if ($logData !== NULL &&

preg_match($searchDomain, $logData)) {

yield $logData;

}

}

}

$fileGeneratorArray = array();

foreach($files as $filename) {

$fileGeneratorArray[] = searchLogData($filename, $pregDomain);

}

PHP 5.5 – Generators$output = fopen('php://output', 'w');

while (!empty($fileGeneratorArray)) {

foreach($fileGeneratorArray as $key => $fileGenerator) {

$result = $fileGenerator->current();

$fileGenerator->next();

if (!$fileGenerator->valid()) {

unset($fileGeneratorArray[$key]);

}

fwrite($output, $result);

}

}


• Additional Reading:

• http://blog.ircmaxell.com/2012/07/what-generators-can-do-for-you.html• http://nikic.github.io/2012/12/22/Cooperative-multitasking-using-coroutines-in-PHP.html

http://blog.ircmaxell.com/2012/07/what-generators-can-do-for-you.html

http://blog.ircmaxell.com/2012/07/what-generators-can-do-for-you.html

http://nikic.github.io/2012/12/22/Cooperative-multitasking-using-coroutines-in-PHP.html

http://nikic.github.io/2012/12/22/Cooperative-multitasking-using-coroutines-in-PHP.html


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Generated Power: PHP 5.5 Generators