Diagnose the reason why write_file doesn't work in CodeIgniter - file

Question

I have the below code.
In my base directory where the main CodeIgniter PHP index file is, I have a directory pagemodules with permission 666.
What I want to do is write in it a file in the following filename format: .main.control.function.var.something.mod
To dynamically create files in this folder I use the below code to check if the file exists, if not, create it with a single space in it.
The only problem is, I come up with a fail every time. I have tried moving the dir into every possible directory to see if it's a file path problem, but that didn't help.
The CodeIgniter wiki isn't much help either because it gives no pointers on how to diagnose errors from the file helper. And no error is thrown whatsoever...
How can I get CodeIgniter to throw an error I can do something with?
I could start working with fopen, but I prefer to use CodeIgniter because of ease of use.
error_reporting(E_ALL);
ini_set("display_errors", 1);
$this->load->helper('file');
if($createfile!=null)
{
$filepath = './pagemodules/'.str_replace('/','.',$data['page']->url).'.mod';
$file = read_file($filepath);
if($file === false)
{
$test = write_file($filepath,' ','w+');
if($test)
{
echo "we have written $filepath";
}
else
{
echo 'fail '.$filepath;
}
}
}

Answer 1

well, just for debug purposes:
Replace './pagemodules/ with 'FCPATH.'pagemodules/ in order to get absolute path to pagemodules (if it is located at index.php codeigniter directory).
To avoid an invalid path, you can use...
get_filenames('path/to/pagemodules/')
...to get its files and corroborate if it is correct.This function return and array with file names into it.
Remember that you can use FCPATH constant to get the absolute path to Codeigniter installation.