Question: mkdir() is working correctly this question is more about catching an error. Instead of printing this when the directory exists I would just like to have it write to a message to me in a custom log. How do I create this exception.

Warning: mkdir() [function.mkdir]: File exists

Answer: 
> 
> I would just like to have it write to a message to me in a custom log.
> 
> 
> 

the solution is very easy. PHP already have everything for you:

```
ini_set('display_errors',0);
ini_set('log_errors',1);
ini_set('error_log','/path/to/custom.log');

```

or same settings in the php.ini or .htaccess  

I think it would be better than write each possible error manually 

If you don't want this error to be logged (as it may be not error but part of application logic), you can check folder existence first

```
if (!file_exists($folder)) mkdir($folder);
else {/*take some appropriate action*/}

```
You can stop the error message from displaying either by suppressing error messages globally (in config or runtime) with the [`display_errors`](http://www.php.net/manual/en/errorfunc.configuration.php#ini.display-errors) setting, or case by case by prefixing the function call with an `@`-character. (E.g. `@mkdir('...')`).

You can then check with [`error_get_last`](http://php.net/manual/en/function.error-get-last.php) when `mkdir` returns `false`. 

For error logging global rules apply. You can log errors manually with [`error_log`](http://php.net/manual/en/function.error-log.php). 

For further reading, see the manual section on [Error handling](http://php.net/manual/en/book.errorfunc.php).

Edit:

As suggested in the comments, a custom error handler is also a possible, arguably more robust (depending on your implementation) but certainly more elegant, solution.

```
function err_handler($errno, $errstr) {
    // Ignore or log error here
}

set_error_handler('err_handler');

```

This way, the error message will not display, unless you explicitly echo it. Note, though, when using a custom error handler `error_get_last` will return `NULL`.