We use unlink() to delete existing files
Before you can delete a file, you must first be sure that it is not open in your program. Use the fclose function to close down an open file.
$myFile = "testFile.txt";
$fh = fopen($myFile, 'w') or die("can't open file");
fclose($fh);
$myFile = "testFile.txt";
unlink($myFile);