src/properties/class-papi-property-dropdown.php
public function format_value( $value, $slug, $post_id ) {
		if ( ! $this->get_setting( 'multiple' ) ) {
			return $this->is_string_items() ? $value : papi_cast_string_value( $value );
		}

		$value = is_array( $value ) ? $value : [];

		if ( ! $this->is_string_items() ) {
			$value = array_map( 'papi_cast_string_value', $value );
		}

		return $value;
	}
public function format_value( $value, $slug, $post_id ) {
		if ( ! $this->get_setting( 'multiple' ) ) {
			return $this->is_string_items() ? $value : papi_cast_string_value( $value );
		}

		$value = is_array( $value ) ? $value : [];

		if ( ! $this->is_string_items() ) {
			$value = array_map( 'papi_cast_string_value', $value );
		}

		return $value;
	}
Format the value of the property before it's returned
to WordPress admin or the site.

@param  mixed  $value
@param  string $slug
@param  int    $post_id

@return mixed