Lexical scoping

Regarding your example:

foreach ($array as &$a) {
$a = 3;
}
$a = null; // $a not a reference anymore. Problem solved :)

Problem not solved. You have just changed the last element of $array...
This is the exact problem that was to be avoided.

unset($a) after the foreach solves the problem.

2014-01-28 Sebastian Krebs krebs.seb@gmail.com

2014-01-28 Andrea Faulds ajf@ajf.me

Good morning,

Perhaps a future version of PHP (PHP 6? 5.7?) could have lexical
scoping
with a
"let" keyword? At the very least, it would make foreach() with a
reference
less
of a problem:

foreach ($array as let &$a) {
    $a = 3;
}
// $a is not in this scope - no need to worry about accidentally

changing
last array item

Any thoughts?

Hi,

My 2 cents: That is a very minor improvement at the cost of an additional
keyword. It is only to avoid, that you accidentally interfere with outers
scope variables? If it is hard to track these variables, maybe your
method/function is too big.

I agree.

Regarding your example:

foreach ($array as &$a) {
$a = 3;
}
$a = null; // $a not a reference anymore. Problem solved :)

Problem not solved. You have just changed the last element of $array...
This is the exact problem that was to be avoided.

AFAIK, this is a problem which is quite limited to foreach() (are there
other examples?), so one (BC-breaking-but-probably-for-the-best) solution
would simply be to unset the variable automatically if it wasn't already
defined:

foreach( $array as &$a ){
$a = 3;
}
var_dump( $a ); // E_NOTICE, $a is now undefined

$b = 2;
foreach( $array as &$b ){
$b = 3;
}
var_dump( $b ); // 3, $b was defined before we started the foreach, so it's
not wiped

Alternatively, you could say that the ultimate problem is that we don't
have strong scoping - braces only define flow control, not scope. So you
could introduce a strong-scoping structure. Maybe a double brace?

foreach( $array as &$a ){{
$a = 3;
}}
var_dump( $a ); // E_NOTICE, $a is now undefined

You could even say that an isolated brace pair (ie not one following a
control statement) always produces a scope.

--GB

2014-01-28 Lazare Inepologlou linepogl@gmail.com

2014-01-28 Sebastian Krebs krebs.seb@gmail.com

2014-01-28 Andrea Faulds ajf@ajf.me

Good morning,

Perhaps a future version of PHP (PHP 6? 5.7?) could have lexical scoping
with a
"let" keyword? At the very least, it would make foreach() with a
reference
less
of a problem:

foreach ($array as let &$a) {
    $a = 3;
}
// $a is not in this scope - no need to worry about accidentally

changing
last array item

Any thoughts?

Hi,

My 2 cents: That is a very minor improvement at the cost of an additional
keyword. It is only to avoid, that you accidentally interfere with outers
scope variables? If it is hard to track these variables, maybe your
method/function is too big.

I agree.

Regarding your example:

foreach ($array as &$a) {
$a = 3;
}
$a = null; // $a not a reference anymore. Problem solved :)

Problem not solved. You have just changed the last element of $array...
This is the exact problem that was to be avoided.

Touche ;)
then use unset(). This time I tried it before:
http://codepad.viper-7.com/lOx1XL

Lazare INEPOLOGLOU
Ingénieur Logiciel

Regards,
Sebastian

--
Andrea Faulds
http://ajf.me/

--

--
github.com/KingCrunch

--
github.com/KingCrunch

2014-01-28 Andrea Faulds ajf@ajf.me

foreach ($array as &$a) {
$a = 3;
}
$a = null; // $a not a reference anymore. Problem solved :)

You just changed the last element of the array to null.

See why I proposed this? ;)

I already fixed this... Read the other messages as well:
http://codepad.viper-7.com/lOx1XL

--
Andrea Faulds
http://ajf.me/

--
github.com/KingCrunch