How to escape this? I'm now using sanitize_text_field(). Was first esc_attr().

gistfile1.php

<?php
	function ajax_save_columns() {
		global $wp_registered_sidebars;

		header( "Content-Type: application/json" );

		if( isset( $_POST['sidebar'], $_POST['amount_columns'] ) && ! empty( $wp_registered_sidebars[ $_POST['sidebar'] ] ) ) {
			$options = get_option( 'horizontal_sidebar_columns', array() );
			$options[ $_POST['sidebar'] ] = absint( $_POST['amount_columns'] );
			update_option( 'horizontal_sidebar_columns', $options );

			echo json_encode( array( 'success' => true ) );
		}
		else {
			echo json_encode( array( 'success' => false ) );
		}

		die();
	}