Generator::send

(PHP 5 >= 5.5.0, PHP 7)

Generator::send — Send a value to the generator

Description

public mixed Generator::send ( mixed $value )

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).

Parameters

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

Return Values

Returns the yielded value.

Examples

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


<?php
function printer() {
    while (true) {
        $string = yield;
        echo $string;
    }
}

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

The above example will output:

Hello world!
Bye world!

User Contributed Notes

sfroelich01 at sp dot gm dot ail dot am dot com

2 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
?>

sergei dot solomonov at gmail dot com

2 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!

kexianbin at diyism dot com

7 months 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