How to create a folder in PHP if it doesn't already exist?

Hello everyone! I'm a beginner PHP developer and I'm writing a site on WordPress. I have a problem: I want to save user-uploaded images to a separate folder for each user. For example, I have a user ID, and I want to create a folder like `/uploads/user_123/`.\n\nI wrote this code:\n\n```php\n$user_id = 123;\n$upload_dir = wp_upload_dir();\n$user_folder = $upload_dir['basedir'] . '/user_' . $user_id . '/';\n\nif (!file_exists($user_folder)) {\n mkdir($user_folder);\n}\n\n// Then copy the file...\nmove_uploaded_file($temp_file, $user_folder . '/avatar.jpg');\n```\n\nBut the problem is that if the folder already exists, `mkdir()` throws a warning "Warning: mkdir(): File exists". I understand that this can be suppressed with `@`, but I've heard that this is bad practice.