Why Union types in PHP? - Purpose & Use Cases

The Big Idea

What if your code could accept different types without messy checks and bugs?

The Scenario

Imagine you are writing a function that can accept either a number or a string. Without union types, you have to write separate functions or add lots of checks everywhere to handle each type manually.

The Problem

This manual approach is slow and error-prone because you must constantly check the type and write duplicate code. It's easy to forget a case or make mistakes, leading to bugs and confusing code.

The Solution

Union types let you declare that a function or variable can accept multiple types directly. This makes your code clearer, safer, and easier to maintain because the language itself knows what types are allowed.

Before vs After

✗ Before

function process($value) {
  if (is_int($value)) {
    // handle int
  } elseif (is_string($value)) {
    // handle string
  } else {
    throw new Exception('Invalid type');
  }
}

✓ After

function process(int|string $value) {
  // handle int or string directly
}

What It Enables

Union types enable writing flexible and robust code that clearly communicates what types are accepted, reducing bugs and improving readability.

Real Life Example

For example, a function that formats user input might accept either a string or an integer ID. Union types let you declare this clearly so the function works smoothly with both.

Key Takeaways

Manual type checks are slow and error-prone.

Union types let you accept multiple types cleanly.

This leads to clearer, safer, and easier-to-maintain code.