How to check if the file input field is empty?

file-upload, input-field, php, validation

Solution

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
}

Problem

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?

Original source