public function get_field_value( $key, $field, $post_data = array() ) {
		$type      = $this->get_field_type( $field );
		$field_key = $this->get_field_key( $key );
		$post_data = empty( $post_data ) ? $_POST : $post_data; // WPCS: CSRF ok, input var ok.
		$value     = isset( $post_data[ $field_key ] ) ? $post_data[ $field_key ] : null;

		if ( isset( $field['sanitize_callback'] ) && is_callable( $field['sanitize_callback'] ) ) {
			return call_user_func( $field['sanitize_callback'], $value );
		}

		// Look for a validate_FIELDID_field method for special handling.
		if ( is_callable( array( $this, 'validate_' . $key . '_field' ) ) ) {
			return $this->{'validate_' . $key . '_field'}( $key, $value );
		}

		// Look for a validate_FIELDTYPE_field method.
		if ( is_callable( array( $this, 'validate_' . $type . '_field' ) ) ) {
			return $this->{'validate_' . $type . '_field'}( $key, $value );
		}

		// Fallback to text.
		return $this->validate_text_field( $key, $value );
	}