请使用此方法：

// Lets create some test CSS code
$css = \'/* Some test CSS */ body {background:red;}\';

// Stash CSS in uploads directory
require_once( ABSPATH . \'wp-admin/includes/file.php\' ); // We will probably need to load this file
global $wp_filesystem;
$upload_dir = wp_upload_dir(); // Grab uploads folder array
$dir = trailingslashit( $upload_dir[\'basedir\'] ) . \'some-folder/\'; // Set storage directory path

WP_Filesystem(); // Initial WP file system
$wp_filesystem->mkdir( $dir ); // Make a new folder for storing our file
$wp_filesystem->put_contents( $dir . \'style.css\', $css, 0644 ); // Finally, store the file :D