Schedule the regular import of files into a WordPress site's wp-content/uploads/ directory

functions.php

<?php

/**
 * Import Files from External Domains v1.0.0
 * 
 * This script is written for WordPress sites.
 * This script can be adapted for use with non WordPress sites.
 * The code in this script should be copied and pasted into a theme's funcitons.php file or into a functionality plugin
 * though it can be used in other ways too.
 * This script does not add files to the WordPress Media Library.
 *
 * Read the comments. You must configure the script or it won't do anything useful.
 *
 * Files are downloaded to wp-content/uploads/$dirname/
 *  Currently configured as wp-content/uploads/importedfiles/
 *  Download location may be different in multisites to e.g. wp-content/uploads/sites/3/$dirname/
 *
 * Old copies of imported files are deleted before new copies are imported.
 *  They are deleted one-by-one, not all at the same time.
 *
 * Copyright Lee Hodson (@vr51) 2021
 *
 **/

function scheduled_file_import_vr51() {
	
	// Configure location of files that are to be imported
	// Add to this array your list of files to be imported. Any file type though must be consistent for all files.
	// Warning: You're responsibile for ensuring the files do not pose a security risk
	// Tip: Google Sheets adds 'gviz/tq?tqx=out:csv' to sheets exported as CSV files;
	
	$importl = array(
		'https://example.com/file1.csv',
		'https://example.com/file2.csv',
		'https://example.com/file3.csv' // no comma for the last file
	);
	
	// Configure the file type extension
	// This is used by CURL when the file is saved
	$ext = 'csv' // File extension
	
	// Optional: Configure the name of directory within wp-uploads that imported files will be downloaded to.
	$dirname = 'importedfiles'; // No leading or trailing forward slash. Enter directory name only.

	// Sometimes required for $wp_filesystem to be accessed.
	// Uncomment the next line if downloads do not happen. This error probably means $wp_filesystem is inaccessible
	// require_once( ABSPATH . 'wp-admin/includes/file.php' ); // this line is needed because this is a functionality plugin
	
	/**
	* Download and store files that will be imported
	*/
	
	// Set the download directory
	$upload_dir = wp_upload_dir();
	$dir = trailingslashit( $upload_dir['basedir'] ) . $direname . '/';

	global $wp_filesystem;
	WP_Filesystem();
	
	// Create $dir if it needs to be created
	if( ! $wp_filesystem->is_dir( $dir ) ) {
		$wp_filesystem->mkdir( $dir ); 
	}
	
	$site = get_site_url(); // Needed for multisite compatibility
	
	// Fetch the $importl files
	
	$n = 1;
	foreach ($importl as $ifile) {
		// Delete previously imported $file if one exists
		unlink( $dir . $n . "import.csv" );
		
		// Fetch new file
		$ch = curl_init();
		curl_setopt($ch, CURLOPT_URL, $ifile);
		curl_setopt($ch, CURLOPT_TRANSFERTEXT, true);
		curl_setopt($ch, CURLOPT_HEADER, false);
		curl_setopt($ch, CURLOPT_REFERER, $site);
		curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
		$csv = curl_exec($ch);
		curl_close($ch);

		// Import the new file and set file permissions to 0644
		$wp_filesystem->put_contents( $dir . $n . 'import.' . $ext, $csv, 0644 );

		$n = $n+1;
	}
}

// Set/Stop the cron event
// Comment out these 5 lines to stop the import cron event
add_action( 'scheduled_file_import_cron', 'scheduled_file_import_vr51' );
if ( ! wp_next_scheduled( 'scheduled_file_import_cron' ) ) {
	// Configure the import time and frequency
	wp_schedule_event( time(), 'daily', 'scheduled_file_import_cron' );
}

// Uncomment the next two lines to delete the scheduled import cron event. 
// $timestamp = wp_next_scheduled( 'scheduled_file_import_cron' );
// wp_unschedule_event( $timestamp, 'scheduled_file_import_cron' );