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Contents
  1. 1. Create generator
  2. 2. Use generator

Requirement PHP 5.5+

  • Generators are simple iterators.
  • Compute and yield iteration values on-demand without commandeering valuable memory.
  • Iterate in only one direction—forward
  • Can’t iterate the same generator more than once

Create generator

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<?php
function myGenerator() {
    yield 'value1';
    yield 'value2';
    yield 'value3';
}

foreach (myGenerator() as $yieldedValue) {
    echo $yieldedValue, PHP_EOL;
}

Output:

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value1
value2
value3

Use generator

Bad to use traditional iterator because it load everything into memory.

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<?php
function makeRange($length) {
    $dataset = [];
    for ($i = 0; $i < $length; $i++) {
        $dataset[] = $i;
    }
    return $dataset;
}
$customRange = makeRange(1000000);
foreach ($customRange as $i) {
    echo $i, PHP_EOL;
}

Good to use generator.

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<?php
function makeRange($length) {
    for ($i = 0; $i < $length; $i++) {
        yield $i;
    }
}
foreach (makeRange(1000000) as $i) {
    echo $i, PHP_EOL;
}

CSV generator.

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<?php
function getRows($file) {
    $handle = fopen($file, 'rb');
    if ($handle === false) {
        throw new Exception();
    }
    while (feof($handle) === false) {
        yield fgetcsv($handle);
    }
    fclose($handle);
}
foreach (getRows('data.csv') as $row) {
    print_r($row);
}
Contents
  1. 1. Create generator
  2. 2. Use generator