3rd snippet in post "Save Multiple Option Values in A Single Database Row"

gistfile1.php

function prfx_sanitize_options( $input ) {
	$input['option_display_mode'] = wp_filter_nohtml_kses( $input['option_display_mode'] );
	$input['option_font_size'] = sanitize_text_field( absint( $input['option_font_size'] ) );
	$input['option_font_color'] = sanitize_text_field( $input['option_font_color'] );
	$input['option_custom_css'] = esc_textarea( $input['option_custom_css'] );
	return $input;
}