Lesson 43 • Advanced

File Storage Abstraction 💾

Abstract file storage with Flysystem to seamlessly switch between local disk, Amazon S3, and cloud providers using one unified API.

What You'll Learn in This Lesson

• Why file storage abstraction prevents vendor lock-in
• Use Flysystem's unified API: write, read, delete, copy, move
• Switch between local and S3 with one config change
• Generate signed URLs for temporary secure access
• Stream large files without exhausting memory

Note: PHP runs on a server. Our examples simulate PHP logic using JavaScript. To run real PHP, install PHP.

🎯 Real-World Analogy: Flysystem is like a universal remote control. Instead of having different remotes for your TV, sound bar, and streaming box, one remote controls them all with the same buttons. Flysystem gives you one API (write, read, delete) that works with local disk, S3, Google Cloud, Azure, FTP — just change which "device" it points at.

Flysystem Unified API

Flysystem provides a single API for all file operations. Write code once against the Filesystem interface, then swap adapters (local, S3, GCS) by changing configuration. This means your app works identically in development (local) and production (S3) without code changes.

Try It: File Storage Operations

Write, read, copy, move, delete, and list files with different adapters

Try it Yourself »

JavaScript

// File Storage Abstraction with Flysystem
console.log("=== Why Abstract File Storage? ===");
console.log();
console.log("  Without abstraction:");
console.log("  ❌ file_put_contents() ties you to local disk");
console.log("  ❌ Switching to S3 means rewriting every file operation");
console.log("  ❌ Can't test without real filesystem");
console.log();
console.log("  With Flysystem:");
console.log("  ✅ Same API for local, S3, GCS, FTP, SFTP, Azure");
console.log("  ✅ Switch storage by changing on
...

Signed URLs & Streaming

Signed URLs provide temporary access to private files — generate a URL that expires in 60 minutes for invoice downloads. For large files (backups, exports), use streaming to avoid loading the entire file into memory. A 2GB file streamed uses only ~8KB of RAM.

Try It: Signed URLs & Multi-Disk

Generate expiring download links and configure multi-disk storage

Try it Yourself »

JavaScript

// Storage Patterns: Signed URLs, Streaming, Multi-disk
console.log("=== Signed URLs (Temporary Access) ===");
console.log();

class SecureStorage {
  constructor(secretKey) { this.secretKey = secretKey; this.files = {}; }

  generateSignedUrl(path, expiresIn) {
    let expires = Date.now() + expiresIn * 1000;
    let signature = btoa(path + ":" + expires + ":" + this.secretKey).substring(0, 16);
    let url = "https://cdn.myapp.com/" + path + "?expires=" + expires + "&sig=" + signature;

    co
...

⚠️ Common Mistakes

⚠️

Storing uploads in the web root — Files in public/ are directly accessible. Store user uploads outside the web root and serve them through a PHP controller that checks permissions.

⚠️

Not setting visibility — S3 objects default to private. If you need public access (avatars), explicitly set visibility: 'public'.

💡

Pro Tip: Use league/flysystem-aws-s3-v3 for S3. In tests, use the InMemory adapter — it's instant and requires no filesystem at all.

📋 Quick Reference — File Storage

Method	Description
write()	Create or overwrite a file
readStream()	Read file as stream (memory efficient)
temporaryUrl()	Generate signed URL with expiration
visibility()	Set public or private access
Adapter	Driver for specific storage (Local, S3, etc.)

🎉 Lesson Complete!

You can now abstract file storage! Next, learn to optimize PHP performance and tune OPcache.