WordPress: Insert multiple files and attach them to post from front-end.

functions.php

<?php 
# Upload multiple files and attach them to post using single function

// Files Uploader attach to shop
if ($_FILES) {	
    $files = $_FILES['shop-imgs'];
    foreach ($files['name'] as $key => $value) {
        if ($files['name'][$key]) {
            $file = array(
	            'name'     => $files['name'][$key],
	            'type'     => $files['type'][$key],
	            'tmp_name' => $files['tmp_name'][$key],
	            'error'    => $files['error'][$key],
	            'size'     => $files['size'][$key]
            );

            $_FILES = array( 'shop-imgs' => $file );
            insert_attachment('shop-imgs', $shop_id);                                  
        }
    }
}


/**
 * This function attaches the image to the post in the database
 */
function insert_attachment($file_handler,$post_id,$setthumb='false') {
	 
	// check to make sure its a successful upload
	if ($_FILES[$file_handler]['error'] !== UPLOAD_ERR_OK) __return_false();
	 
	require_once(ABSPATH . "wp-admin" . '/includes/image.php');
	require_once(ABSPATH . "wp-admin" . '/includes/file.php');
	require_once(ABSPATH . "wp-admin" . '/includes/media.php');
	 
	$attach_id = media_handle_upload( $file_handler, $post_id );
	 
	if ($setthumb) update_post_meta($post_id,'_thumbnail_id',$attach_id);
		return $attach_id;
}

?>