PHP file operation_PHP tutorial

if(!is_dir('txt'))//Determine whether txt is a folder directory
{
mkdir('txt');//Create a folder directory named txt
$open=fopen('txt/in.txt',"w+");//Open the file for reading and writing
If(is_writable('txt/in.txt'))//If this file is in writable mode
           {
If(fwrite($open,"Today is a beautiful day, you must be happy! "- -"")>0)//Write content
           fclose($open);//Close the file
echo "<script>alert('Writing successful');</script>";//Output success prompt
}
}
else
          {
If(is_file('txt/in.txt'))//Determine whether the in.txt file exists in the directory
                {
If(is_readable('txt/in.txt'))//Determine whether the file is readable
                                                               {
                                      echo file_get_contents('txt/in.txt');//Output text information
                        unlink('txt/in.txt');//Delete file in.txt
                                                                                                                                                                                                                  rmdir('txt');//Delete directory
                 }
            }
}
?>

Excerpted from ms.元