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Date: Sun, 11 May 2003 16:40:51 +0100
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Message-ID: <200305111640.51779.postmaster@terrarium.f9.co.uk>
Sender: Theo Spears <grendels@terrarium.f9.co.uk>
Subject: Re: [PHP-DEV] exceptions instead of errors
From: postmaster@terrarium.f9.co.uk (Theo Spears)

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 =3D mysql_connect("localhost", "user", "pass");
>   $sth =3D mysql_query("select bar from foo", $m);
>   while ($row =3D 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=20
it would give everyone big problems when it comes to predicting the control=
=20
flow of their programs. For example

function db_connect ( $db_name ) {
  $link =3D 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=20

db_connect ( 'foo' );

The function will behave differently. Even if all new PHP5 code uses=20
exceptions there is a lot of code which doesn't, and so the principles of=20
information hiding say you would have to make sure any code which calls a=20
function in a separate module has to make sure that function isn't inside a=
=20
try{}catch{} block, and the only functions in the same module which are=20
inside try{}catch{} blocks that catch internal exceptions don't call any=20
functions in external modules.

Personally I would prefer a system similar to the @ notation which suppress=
es=20
error messages, possibly make %function() or similar cause the function to=
=20
raise an exception. (The engine could handle this by silently dropping all=
=20
exceptions from internal functions that weren't called with the relevant=20
prefix).

Just my =A30.02

Theo Spears