PHP on IIS FOPEN permission denied

I'm trying to either write or create a file, but I keep getting a permission denied error.

failed to open stream: Permission denied [file]

I did the following already:

In the php.ini file :
allow_url_fopen = on
allow_url_include = on
file_uploads = on

On the server:
IIS_IUSR has FULL CONTROL permission which allows:
traverse folder/execute file
list folder/read data
read attribute
read extended attributes
create files/write data
create folders/append data
write attributes
write extended attributes
delete subfolder and files
delete
read permissions
change permissions
take ownership

In my code I've tried:
$file = fopen( $GLOBAL_FILEPATH, 'wb' );
$file = fopen( $GLOBAL_FILEPATH, 'w' );
$file = fopen( $GLOBAL_FILEPATH, 'w+' );

I can read from the file, so that ensures that my directory path is correct.

No luck.  Any help would be greatly appreciated.