utility_types.md

Utility types

Psalm supports some magical utility types that brings superpower to the PHP type system.

properties-of<T>

This collection of utility types construct a keyed-array, with the names of non-static properties of a class as keys, and their respective types as values. This can be useful if you need to convert objects into arrays.

class A {
  public string $foo;
  public int $bar;

  /**
   * @return properties-of<self>
   */
  public function asArray(): array {
    return [
      'foo' => $this->foo,
      'bar' => $this->bar,
    ];
  }

  /**
   * @return list<key-of<properties-of<self>>>
   */
  public function attributeNames(): array {
    return ['foo', 'bar']
  }
}

Variants

Note that properties-of<T> will return all non-static properties. There are the following subtypes to pick only properties with a certain visibility:

• public-properties-of<T>
• protected-properties-of<T>
• private-properties-of<T>