Serialization and Debugging

📦 PHP Serialization & Debugging: The Magic Suitcase Adventure

Imagine you have a magical suitcase that can shrink your toys, pack them as a secret code, and later bring them back exactly as they were. That’s serialization in PHP!

🎯 What You’ll Learn

• Object Serialization – Turning objects into storable strings
• Object Unserialization – Bringing objects back to life
• Debugging with var_dump – Peeking inside your variables
• Error Logging – Keeping a diary of what goes wrong

🧳 Object Serialization: Packing Your Toy Box

The Story

Think of your favorite toy robot. It has a name, a color, and special powers. Now imagine you want to send this robot to your friend through a tiny mailbox. The robot is too big!

Serialization is like a magic spell that turns your robot into a flat letter (a string of text). This letter contains ALL the information about your robot – its name, color, and powers – written in a special code.

Why Do We Need This?

• 📧 Save data to files – Store objects for later
• 🗄️ Put in databases – Save complex data easily
• 🌐 Send over the internet – Share objects between systems
• 💾 Cache information – Speed up your app

Simple Example

<?php
// Our toy robot class
class Robot {
    public $name;
    public $color;
    public $power;

    public function __construct($name, $color, $power) {
        $this->name = $name;
        $this->color = $color;
        $this->power = $power;
    }
}

// Create a robot
$myRobot = new Robot("Bolt", "Blue", 100);

// SERIALIZE: Turn robot into a string!
$packedRobot = serialize($myRobot);

echo $packedRobot;
// Output: O:5:"Robot":3:{s:4:"name";s:4:"Bolt";...}
?>

What Does That Code Mean?

O:5:"Robot" → Object named "Robot" (5 letters)
:3:         → Has 3 properties
{...}       → The packed data inside

It’s like a recipe that tells PHP exactly how to rebuild your robot later!

🔮 Object Unserialization: Unpacking the Magic

The Story Continues

Your friend received that magical letter (the serialized string). Now they want to play with the robot! Unserialization is the reverse spell – it reads the secret code and rebuilds the exact same robot.

Bringing Objects Back to Life

<?php
// The packed robot string (from before)
$packedRobot = 'O:5:"Robot":3:{s:4:"name";...}';

// UNSERIALIZE: Bring robot back!
$myRobot = unserialize($packedRobot);

// It's alive again!
echo $myRobot->name;  // Output: Bolt
echo $myRobot->color; // Output: Blue
?>

⚠️ Safety Warning!

Never unserialize data from strangers! It’s like opening a package from someone you don’t know – it might have something bad inside.

<?php
// ❌ DANGEROUS - Never do this!
$badData = $_GET['data'];
$object = unserialize($badData);

// ✅ SAFE - Only unserialize trusted data
$trustedData = file_get_contents('my_saved_data.txt');
$object = unserialize($trustedData);
?>

Magic Methods: __sleep() and __wakeup()

These are like bedtime and wake-up routines for your objects!

<?php
class Robot {
    public $name;
    public $battery;
    private $secretCode;

    // Runs BEFORE serialization (bedtime!)
    public function __sleep() {
        // Don't pack the secret code
        return ['name', 'battery'];
    }

    // Runs AFTER unserialization (wake up!)
    public function __wakeup() {
        // Reconnect to power source
        $this->battery = 100;
    }
}
?>

🔍 Debugging with var_dump: The X-Ray Vision

The Story

Sometimes your code doesn’t work, and you feel lost. It’s like having a box and not knowing what’s inside. var_dump() is your X-ray glasses – it shows you EVERYTHING inside a variable!

Your Debugging Superpower

<?php
$mystery = ["apple", 42, true, null];

var_dump($mystery);

Output:

array(4) {
  [0]=> string(5) "apple"
  [1]=> int(42)
  [2]=> bool(true)
  [3]=> NULL
}

var_dump vs echo vs print_r

Real Detective Work

<?php
class User {
    public $name = "Alice";
    private $password = "secret123";
    protected $role = "admin";
}

$user = new User();
var_dump($user);

Output:

object(User)#1 (3) {
  ["name"]=> string(5) "Alice"
  ["password":"User":private]=> string(9) "secret123"
  ["role":protected]=> string(5) "admin"
}

See? var_dump shows you even the secret stuff!

Pro Tips for var_dump

<?php
// Tip 1: Use <pre> for pretty output
echo "<pre>";
var_dump($complexData);
echo "</pre>";

// Tip 2: Stop code after dumping
var_dump($data);
die(); // or exit();

// Tip 3: Dump multiple things at once
var_dump($var1, $var2, $var3);
?>

📝 Error Logging: Your Code’s Diary

The Story

Imagine you’re a detective, and every night, your assistant writes down everything unusual that happened. Error logging is exactly that – PHP keeps a diary of problems so you can solve them later!

Why Not Just Show Errors on Screen?

• 👤 Users shouldn’t see ugly error messages
• 🔒 Errors might reveal secret information
• 📊 Logs help you find patterns
• 🕐 You can check problems that happened at 3 AM!

Setting Up Your Error Diary

<?php
// Where to save the diary
ini_set('log_errors', 1);
ini_set('error_log', '/path/to/my-errors.log');

// Don't show errors on screen (for live sites)
ini_set('display_errors', 0);
?>

Writing to Your Diary

<?php
// Write a custom message to the log
error_log("User tried to access secret page!");

// Log with more details
$userId = 42;
error_log("User $userId failed login at " . date('Y-m-d H:i:s'));
?>

In your log file:

[21-Dec-2025 10:30:15] User tried to access secret page!
[21-Dec-2025 10:30:16] User 42 failed login at 2025-12-21 10:30:16

Error Levels Explained Simply

graph TD
    A["🔴 FATAL ERROR"] --> B["App Stops Working"]
    C["🟠 WARNING"] --> D["Something Wrong, But Continues"]
    E["🟡 NOTICE"] --> F["Small Issue, Might Cause Problems"]
    G["🔵 DEPRECATED"] --> H["Works Now, But Use New Way Soon"]

Complete Error Logging Setup

<?php
// Error reporting level
error_reporting(E_ALL);

// Log ALL errors
ini_set('log_errors', 1);

// Custom log file location
ini_set('error_log', __DIR__ . '/logs/app.log');

// For DEVELOPMENT: Show errors
ini_set('display_errors', 1);

// For PRODUCTION: Hide errors
// ini_set('display_errors', 0);

// Custom error handler (advanced!)
set_error_handler(function($level, $message, $file, $line) {
    $log = "[" . date('Y-m-d H:i:s') . "] ";
    $log .= "Level: $level | ";
    $log .= "Message: $message | ";
    $log .= "File: $file | Line: $line";

    error_log($log);
    return true;
});
?>

🎮 Quick Reference Flow

graph TD
    A["PHP Object"] -->|serialize| B["String"]
    B -->|Save to file/DB| C["Storage"]
    C -->|Load from file/DB| D["String"]
    D -->|unserialize| E["PHP Object"]

    F["Any Variable"] -->|var_dump| G["See Everything Inside"]

    H["Error Happens"] -->|error_log| I["Log File"]
    I -->|Read Later| J["Fix Problems"]

🎉 What You’ve Learned!

💡 Remember This!

Serialization is packing your toys into a magic suitcase. Unserialization is opening that suitcase and finding your toys exactly as they were. var_dump is your X-ray glasses to see inside anything. Error logging is your helper writing down problems while you sleep.

You’re now a PHP debugging wizard! 🧙‍♂️✨