src/core/class-papi-core-property.php
public function update_value( $value, $slug, $post_id ) {
		if ( ! ( $value = $this->prepare_value( $value ) ) ) {
			return;
		}

		return papi_maybe_json_encode( $value );
	}
public function update_value( $value, $slug, $post_id ) {
		if ( ! ( $value = $this->prepare_value( $value ) ) ) {
			return;
		}

		return papi_maybe_json_encode( $value );
	}
Update value before it's saved to the database.

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

@return mixed