Lizzy McOOP

Magic Methods

special methods PHP calls automatically when certain events happen to an object; they always start with a double underscore (__).

Automatic

you never call magic methods directly; PHP triggers them for you.

Reserved names

fixed names like __get; you should not invent your own methods.

Powerful

Control creation, property access, printing, cloning and more.

__construct

runs when an object is created; use it to set initial state.

__destruct

runs when the object is destroyed or the script ends; use it to clean up (close files, connections). Not guaranteed to run on fatal errors — don’t rely on it for critical work.

Constructor promotion (PHP 8)

declares and assigns properties in one step inside the constructor.

__get

called when reading an inaccessible (private/undefined) property.

__set

called when writing an inaccessible (private/undefined) property; great for validation and controlled access.

__toString

defines how an object behaves as a string (echo, concatenation); must return a string.

__invoke

lets you call an object like a function; suits callbacks like array_map().

__call

handles calls to undefined or inaccessible instance methods.

__callStatic

does the same as __call but for static methods; useful for dynamic APIs and proxies.

__clone

runs on the new copy after using the clone keyword; use it to make a deep copy so nested objects aren’t shared (a plain clone is shallow — nested objects stay shared).

__isset

runs when _____ or empty() is used on an inaccessible property; without it, _____ on hidden properties returns false.

__unset

runs when ____ is used on an inaccessible property.

Exception

an unexpected event that interrupts normal program flow (e.g. file not found, division by zero, database error).

try

the block where you place code that might cause an error.

catch

handles the error if one happens.

finally

runs always, whether or not an error happened.

DivisionByZeroError

thrown when dividing a number by zero.

TypeError

thrown when passing the wrong data type to a function.

ValueError

thrown when a value has a valid type but an invalid value.

ParseError

thrown for syntax errors in code.

Throwable

the parent of both Exception and Error; catching it catches both.

Use specific exception classes

create different custom exceptions for different errors.

Catch only what you can handle

avoid catching exceptions you can’t properly handle.

Use finally for cleanup

always use finally to close files, DB connections, or show a message.

Avoid silent fails

never catch errors without logging or notifying.

Namespace

like a folder or container for your code; organizes classes, functions, and constants and avoids name conflicts between parts of your program or with external libraries.

Why namespaces are needed

without them, two classes with the same name (e.g. two User classes) in the same project cause PHP to throw an error since it can’t tell which one you mean.

use keyword

imports a namespaced class so you don’t have to write the full path every time; can also be used to give it an alias.

Avoids conflicts (namespace benefit)

prevents name collisions between classes/functions.

Organized structure (namespace benefit)

groups related code logically.

Readable code (namespace benefit)

makes a class’s purpose and location obvious.

Autoloading support (namespace benefit)

works seamlessly with Composer and PSR-4.

Team-friendly (namespace benefit)

reduces merge and naming issues in teams.

Reusable modules (namespace benefit)

lets you reuse components across projects.

Safe package use (namespace benefit)

allows multiple third-party libraries to be used safely together.

Autoloading

PHP automatically loads class files when you use a class, so you don’t need to write require or include for every class manually.

spl_autoload_register()

lets you register a custom function that tells PHP how to find and load class files whenever a class is used.

PSR-4

the official PHP Standard Recommendation (#4) that defines how to automatically load classes from file paths based on their namespaces; published by PHP-FIG. In simple terms: Namespace = Folder, Class Name = File Name.

Composer

a dependency/autoloading tool; you define your namespace mapping in composer.json, then run composer dump-autoload to generate a vendor/ folder and vendor/autoload.php.

composer.json

the file where you declare the root namespace prefix (e.g. “App\”) and the folder it maps to (e.g. “src/App/”).