How to check if the file input field is empty?

Question

I am having a hard time using $_FILES

I want to check if file upload field is empty or not then apply a condition such that if file upload is empty then the script doesn't try uploading the file. How do I enforce this?

Answer 1

if($_FILES["file"]["error"] != 0) {
//stands for any kind of errors happen during the uploading
} 

also there is

if($_FILES["file"]["error"] == 4) {
//means there is no file uploaded
}