# PHP Generators

Generators provide an easy way to implement simple iterators without the overhead or complexity of implementing a class that implements the `Iterator` interface.

A generator allows you to write code that uses `foreach` to iterate over a set of data without needing to build an array in memory, which may cause you to exceed a memory limit.

---

## 1. The `yield` Keyword
A generator function looks just like a normal function, except that instead of returning a value, a generator `yield`s as many values as it needs to.

When a generator function is called, it returns an object that can be iterated over.

```php
function simpleGenerator() {
    yield 1;
    yield 2;
    yield 3;
}

foreach (simpleGenerator() as $value) {
    echo $value . "\n";
}
```

## 2. Why Use Generators? (Memory Efficiency)
The primary benefit is memory usage. If you need to iterate over a large range of numbers or lines in a file, an array stores them all in memory at once. A generator yields them one by one.

### Using an Array (High Memory)
```php
function getRange($max) {
    $array = [];
    for ($i = 0; $i < $max; $i++) {
        $array[] = $i;
    }
    return $array;
}
```

### Using a Generator (Low Memory)
```php
function getRangeGenerator($max) {
    for ($i = 0; $i < $max; $i++) {
        yield $i;
    }
}

// This uses constant memory regardless of $max
foreach (getRangeGenerator(1000000) as $number) { ... }
```

[[programming/php/php]] [[programming/php/php-loops]]