Generator::send

(PHP 5 >= 5.5.0, PHP 7)

Generator::sendSend a value to the generator

Beschreibung

public Generator::send ( mixed $value ) : mixed

Sends the given value to the generator as the result of the current yield expression and resumes execution of the generator.

If the generator is not at a yield expression when this method is called, it will first be let to advance to the first yield expression before sending the value. As such it is not necessary to "prime" PHP generators with a Generator::next() call (like it is done in Python).

Parameter-Liste

value

Value to send into the generator. This value will be the return value of the yield expression the generator is currently at.

R├╝ckgabewerte

Returns the yielded value.

Beispiele

Beispiel #1 Using Generator::send() to inject values

<?php
function printer() {
    echo 
"I'm printer!".PHP_EOL;
    while (
true) {
        
$string yield;
        echo 
$string.PHP_EOL;
    }
}

$printer printer();
$printer->send('Hello world!');
$printer->send('Bye world!');
?>

Das oben gezeigte Beispiel erzeugt folgende Ausgabe:

I'm printer!
Hello world!
Bye world!

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User Contributed Notes 5 notes

up
57
sfroelich01 at sp dot gm dot ail dot am dot com
6 years ago
Reading the example, it is a bit difficult to understand what exactly to do with this. The example below is a simple example of what you can do this.

<?php
function nums() {
    for (
$i = 0; $i < 5; ++$i) {
               
//get a value from the caller
       
$cmd = (yield $i);
       
        if(
$cmd == 'stop')
            return;
//exit the function
       
}    
}

$gen = nums();
foreach(
$gen as $v)
{
    if(
$v == 3)//we are satisfied
       
$gen->send('stop');
   
    echo
"{$v}\n";
}

//Output
0
1
2
3
?>
up
10
sergei dot solomonov at gmail dot com
6 years ago
<?php
function foo() {
   
$string = yield;
    echo
$string;
    for (
$i = 1; $i <= 3; $i++) {
        yield
$i;
    }
}

$generator = foo();
$generator->send('Hello world!');
foreach (
$generator as $value) echo "$value\n";
?>

This code falls with the error:
PHP Fatal error:  Uncaught exception 'Exception' with message 'Cannot rewind a generator that was already run'.
foreach internally calls rewind, you should remember this!
up
1
baohx2000 at gmail dot com
1 month ago
I have found that inverse generators (using $x = yield) is a great way to handle chunked batch processing. As data is being iterated, once a specific count has been fed to the generator, it processes and resets the data. For example, you could do a batch mysql insert every 500 records.

Example (note the handling of null, which you would send to the generator to handle stragglers after the previous batch)

function importer()
{
  $max = 500;
  $items = [];
  while (true) {
    $item = yield;
    if ($item !== null) {
      $items[] = yield;
    }
    if ($item === null || count($items) >= $max) {
       // do batch operations
       $items = [];
    }
  }
}
up
0
anonymous at example dot com
5 months ago
As of 7.3, the behavior of a generator in a foreach loop depends on whether or not it expects to receive data. Relevant if you are experiencing "skips".

<?php
class X implements IteratorAggregate {
    public function
getIterator(){
        yield from [
1,2,3,4,5];
    }
    public function
getGenerator(){
        foreach (
$this as $j => $each){
            echo
"getGenerator(): yielding: {$j} => {$each}\n";
           
$val = (yield $j => $each);
            yield;
// ignore foreach's next()
           
echo "getGenerator(): received: {$j} => {$val}\n";
        }
    }
}
$x = new X;

foreach (
$x as $i => $val){
    echo
"getIterator(): {$i} => {$val}\n";
}
echo
"\n";

$gen = $x->getGenerator();
foreach (
$gen as $j => $val){
    echo
"getGenerator(): sending:  {$j} => {$val}\n";
   
$gen->send($val);
}
?>

getIterator(): 0 => 1
getIterator(): 1 => 2
getIterator(): 2 => 3
getIterator(): 3 => 4
getIterator(): 4 => 5

getGenerator(): yielding: 0 => 1
getGenerator(): sending:  0 => 1
getGenerator(): received: 0 => 1
getGenerator(): yielding: 1 => 2
getGenerator(): sending:  1 => 2
getGenerator(): received: 1 => 2
getGenerator(): yielding: 2 => 3
getGenerator(): sending:  2 => 3
getGenerator(): received: 2 => 3
getGenerator(): yielding: 3 => 4
getGenerator(): sending:  3 => 4
getGenerator(): received: 3 => 4
getGenerator(): yielding: 4 => 5
getGenerator(): sending:  4 => 5
getGenerator(): received: 4 => 5
up
-9
kexianbin at diyism dot com
4 years ago
an example:

$coroutine=call_user_func(create_function('', <<<'fun_code'
    echo "inner 1:\n";
    $rtn=(yield 'yield1');
    echo 'inner 2:';var_export($rtn);echo "\n";
    $rtn=(yield 'yield2');
    echo 'inner 3:';var_export($rtn);echo "\n";
    $rtn=(yield 'yield3');
    echo 'inner 4:';var_export($rtn);echo "\n";
fun_code
));
echo ":outer 1\n";                                       // :outer 1
var_export($coroutine->current());echo ":outer 2\n";     // inner 1:, 'yield1':outer 2
var_export($coroutine->current());echo ":outer 3\n";     // 'yield1':outer 3
var_export($coroutine->next());echo ":outer 4\n";        // inner 2:NULL, NULL:outer 4
var_export($coroutine->current());echo ":outer 5\n";     // 'yield2':outer 5
var_export($coroutine->send('jack'));echo ":outer 6\n";  // inner 3:'jack', 'yield3':outer 6
var_export($coroutine->current());echo ":outer 7\n";     // 'yield3':outer 7
var_export($coroutine->send('peter'));echo ":outer 8\n"; // inner 4:'peter', NULL:outer 8
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