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Date: Sun, 11 May 2003 18:52:31 +0200
To: Theo Spears <postmaster@terrarium.f9.co.uk>
Cc: internals@lists.php.net
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Subject: Re: [PHP-DEV] exceptions instead of errors
From: marcus.boerger@t-online.de ((Marcus =?iso-8859-1?Q?B=F6rger?=))

At 17:40 11.05.2003, Theo Spears wrote:
>On Sunday 04 May 2003 20:48, Sterling Hughes wrote:
> > Just a note that I'd really like to see this.  One of the great things
> > about exceptions will be:
> >
> > try {
> >   $m = mysql_connect("localhost", "user", "pass");
> >   $sth = mysql_query("select bar from foo", $m);
> >   while ($row = mysql_fetch_array($sth)) {
> >     echo $row[0];
> >   }
> >   mysql_close($m);
> > } catch (exception $e) {
> >   echo $e->getMessage();
> > }
> >
> > This allows you to remove all the nasty if ($conn) could, and move your
> > error handling into a singular place. I *really* would like this for
> > internal functions.  We could also make a new type of exception
> > "internalexception," which a user has to specifically catch.  This way
> > unless you explictly specify that you want to catch an
> > internalexception, it will default to just outputting an error message.
> >
>Although this approach would certainly simplify handling errors it seems 
>to me
>it would give everyone big problems when it comes to predicting the control
>flow of their programs. For example
>
>function db_connect ( $db_name ) {
>   $link = mysql_connect();
>   if ( ! mysql_select_db( $db_name, $link ) ) {
>     mysql_select_db ( BACKUP_DB_NAME, $link );
>   }
>}
>
>now, depending on whether you do
>
>try {
>   db_connect ( 'foo' );
>} catch (exception e) {
>}
>
>or just
>
>db_connect ( 'foo' );
>
>The function will behave differently. Even if all new PHP5 code uses
>exceptions there is a lot of code which doesn't, and so the principles of
>information hiding say you would have to make sure any code which calls a
>function in a separate module has to make sure that function isn't inside a
>try{}catch{} block, and the only functions in the same module which are
>inside try{}catch{} blocks that catch internal exceptions don't call any
>functions in external modules.
>
>Personally I would prefer a system similar to the @ notation which suppresses
>error messages, possibly make %function() or similar cause the function to
>raise an exception. (The engine could handle this by silently dropping all
>exceptions from internal functions that weren't called with the relevant
>prefix).


The rule "try/catch = exception" would be easy enough to understand.
Changing all code to use exceptions would also work since the bahaviour
would fall back to the normal one if you missed to define a try/catch block.

marcus