Why Intersection types in PHP? - Purpose & Use Cases

The Big Idea

What if your code could automatically guarantee objects have all the features you need, without messy checks?

The Scenario

Imagine you have a function that needs an object which is both a Logger and a Serializer. Without intersection types, you must manually check and combine these capabilities, making your code messy and hard to maintain.

The Problem

Manually verifying that an object meets multiple interfaces means writing extra checks and error handling everywhere. This slows development and increases bugs because you might forget a check or mix up types.

The Solution

Intersection types let you declare that a value must satisfy multiple types at once. This means the language enforces the object has all required features, making your code cleaner and safer.

Before vs After

✗ Before

$obj = getObject();
if (!($obj instanceof Logger) || !($obj instanceof Serializer)) {
    throw new Exception('Invalid object');
}

✓ After

function process(Logger&Serializer $obj) {
    // $obj is guaranteed to be both Logger and Serializer
}

What It Enables

It enables writing precise and safe code that works only with objects having multiple required capabilities, reducing bugs and improving clarity.

Real Life Example

When building a system that logs data and also converts it to JSON, intersection types ensure the object you pass can do both without extra checks.

Key Takeaways

Manual checks for multiple types are slow and error-prone.

Intersection types enforce multiple type requirements at once.

This leads to cleaner, safer, and more maintainable code.