Generators

Quick Introduction

Generators is a single PHP idea you'll use in almost every backend project.

In this lesson you learn only generators — not five topics at once. By the end you can write a small working example and explain it in an interview.

We connect each lesson to our course projects: Login System, Blog CMS, REST API, Inventory, Employee Management, and E-Commerce Backend.

Business Problem

You're building the REST API. After a user signs in, you need generators working correctly before storing data or showing a dashboard.

Without understanding Generators, the team ships bugs: wrong totals, broken sessions, or type errors that only appear in production. This lesson fixes that with one clear pattern you can copy into your project today.

Core Concept

• Generators is one focused idea — learn it before mixing with other PHP topics.
• Use it in PHP 8.3+ with declare(strict_types=1); at the top of every file.
• Our course project (REST API) uses generators in real handlers.
• Run small scripts with php file.php after each change — don't just read.
• Interviewers ask for a one-minute explanation plus a tiny code sample.

Syntax

Core syntax for Generators. Every keyword below appears in production PHP — Laravel and Symfony use the same primitives under the hood.

declare(strict_types=1);

Keywords: declare · strict_types · namespace

Step-by-Step Example

Run this script locally. Change one value, run again, and watch what changes.

<?php
declare(strict_types=1);

function readCsvRows(string $path): Generator {
    $handle = fopen($path, 'r');
    if ($handle === false) {
        throw new RuntimeException("Cannot open {$path}");
    }
    try {
        while (($row = fgetcsv($handle)) !== false) {
            yield $row;
        }
    } finally {
        fclose($handle);
    }
}

$total = 0;
foreach (readCsvRows(__DIR__ . '/orders.csv') as [$sku, $qty, $price]) {
    $total += (int)$qty * (float)$price;
}
echo "Revenue: {$total}\n";

Line by line

1. — part of the generators example; run the file to see the result.
2. declare(strict_types=1); — turns on strict type checking for this file.
3. function readCsvRows(string $path): Generator { — part of the generators example; run the file to see the result.
4. $handle = fopen($path, 'r'); — part of the generators example; run the file to see the result.
5. if ($handle === false) { — part of the generators example; run the file to see the result.

Generators OK

Real-World Example

In the REST API, generators appears in a single request handler — not spread across ten files. Keep the example small, test it with php, then paste the pattern into your project branch.

<?php
declare(strict_types=1);

// TODO: Generators exercise for REST API