public function getChildKeys(): array
    {
        $snapshot = $this->shallow()->getSnapshot();

        if (\is_array($value = $snapshot->getValue())) {
            return array_keys($value);
        }

        throw new OutOfRangeException(sprintf('%s has no children with keys', $this));
    }
public function getChildKeys(): array
    {
        $snapshot = $this->shallow()->getSnapshot();

        if (\is_array($value = $snapshot->getValue())) {
            return array_keys($value);
        }

        throw new OutOfRangeException(sprintf('%s has no children with keys', $this));
    }
public function getChildKeys ( ) : array { $ snapshot = $ this -> shallow ( ) -> getSnapshot ( ) ; if ( \ is_array ( $ value = $ snapshot -> getValue ( ) ) ) { return array_keys ( $ value ) ; } throw new OutOfRangeException ( sprintf ( '%s has no children with keys' , $ this ) ) ; }
Returns the keys of a reference's children.

@throws OutOfRangeException if the reference has no children with keys
@throws ApiException if the API reported an error

@return string[]
Returns the keys of a reference s children .