Multi-Tenant SaaS

Quick Introduction

Multi-Tenant SaaS is a single PHP idea you'll use in almost every backend project.

In this lesson you learn only multi-tenant saas — 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 E-Commerce Backend. After a user signs in, you need multi-tenant saas working correctly before storing data or showing a dashboard.

Without understanding Multi-Tenant SaaS, 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

• Multi-Tenant SaaS 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 (E-Commerce Backend) uses multi-tenant saas 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 Multi-Tenant SaaS. 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);

final readonly class TenantContext {
    public function __construct(public string $tenantId, public string $schema) {}
}

final class TenantConnectionFactory {
    public function forTenant(TenantContext $tenant): \PDO {
        $dsn = "mysql:host=127.0.0.1;dbname={$tenant->schema}";
        $pdo = new \PDO($dsn, 'app', 'secret', [\PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION]);
        $pdo->exec("SET @tenant_id = " . $pdo->quote($tenant->tenantId));
        return $pdo;
    }
}

$tenant = new TenantContext('org_acme', 'tenant_acme');
$pdo = (new TenantConnectionFactory())->forTenant($tenant);
$stmt = $pdo->query('SELECT COUNT(*) FROM users');
echo 'Users: ' . $stmt->fetchColumn();

Line by line

1. — part of the multi-tenant saas example; run the file to see the result.
2. declare(strict_types=1); — turns on strict type checking for this file.
3. final readonly class TenantContext { — part of the multi-tenant saas example; run the file to see the result.
4. public function __construct(public string $tenantId, public string $schema) {} — part of the multi-tenant saas example; run the file to see the result.
5. } — part of the multi-tenant saas example; run the file to see the result.

{"status":"ok"}

Real-World Example

In the E-Commerce Backend, multi-tenant saas 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: Multi-Tenant SaaS exercise for E-Commerce Backend