insert new image into new post on frontend submit

I need some help on inserting new image into new post, I have a front-end submitter to add new posts but my images come from a base64_image when I submit the form both the post and the images are posted but I can’t seem to figure out how to insert the image into the post and set it as featured image also on submit

my post info is set like this

$post_information = array(
		'post_title' => esc_attr(strip_tags($_POST['postTitle'])),
		'post_content' => esc_attr(strip_tags($_POST['postContent'])),
		'post_type' => 'product',
		'post_status' => 'publish',
         );

	$post_id = wp_insert_post( $post_information);
			   update_post_meta( $post_id, '_regular_price', strip_tags($_POST['_regular_price'] ) ) ;
			   update_post_meta( $post_id, '_price', strip_tags($_POST['_regular_price'] ));

};

and if my image is base64 it is converted and uloaded to media gallery with this code

if($_POST['base64Image'] != ''){
	// Create (and CHMOD) a directory to hold temporary image files...
	if (!is_dir(dirname(__FILE__) . '/temp_images')){
		mkdir(dirname(__FILE__) . '/temp_images/');
		chmod(dirname(__FILE__) . '/temp_images/', 0777);
	}

	// Save a temporary version of the image based on the base64 supplied...
	define('UPLOAD_DIR', dirname(__FILE__) . '/temp_images/');
	$img = $_POST['base64Image'];
	$img = str_replace('data:image/png;base64,', '', $img);
	$img = str_replace(' ', '+', $img);
	$data = base64_decode($img);
	$file = UPLOAD_DIR . uniqid() . '.png';
	$success = file_put_contents($file, $data);

	// Create a $_FILES based array...
	$file_array['tmp_name'] = $file;
	$file_array['name'] = 'image.png'; 

	// Include required files...
	require_once(ABSPATH . 'wp-admin/includes/file.php');
	require_once(ABSPATH . 'wp-admin/includes/media.php');
	require_once(ABSPATH . 'wp-admin/includes/image.php');

	// Move the file to the uploads directory...
	$uploadedfile = $file_array;
	$upload_overrides = array('test_form' => false);
	$movefile = wp_handle_sideload($uploadedfile, $upload_overrides);
	// If the move was successful...
if ($movefile){
	// Remove the temp image file...
	@unlink($file_array['tmp_name']);

	// Generate image metadata...
	$wp_filetype = wp_check_filetype(basename($movefile['file']), null);
	$wp_upload_dir = wp_upload_dir();
	$attachment = array(
		'guid' => $wp_upload_dir['url'] . '/' . basename( $movefile['file']),
		'post_mime_type' => $wp_filetype['type'],
		'post_title' => preg_replace('/\.[^.]+$/', '', basename($movefile['file'])),
		'post_content' => '',
		'post_status' => 'inherit'
	);

	// Add the image into the media library...
	$attach_id = wp_insert_attachment($attachment, $movefile['file']);
	$attach_data = wp_generate_attachment_metadata($attach_id, $movefile['file']);
	wp_update_attachment_metadata($attach_id, $attach_data);

}

}

Any help will be appreciated