Can a trait define abstract methods, and how does this let a trait enforce that any class using it must provide its own specific implementation of certain behavior?

A trait can define an abstract method, meaning it declares the method's name and signature without providing any actual implementation body, which forces any class that uses that trait to provide its own concrete implementation of that specific method, and this pattern is useful when a trait provides some shared, general behavior but also depends on a piece of information or logic that can only reasonably be supplied by each individual class using it, such as needing to know the specific name of a database table.

trait Searchable {
    abstract public function getSearchableFields(): array;

    public function search(string $term): array {
        // uses getSearchableFields() internally
    }
}