in Operator View as Markdown

Hello Niklas,

Hello,

I'd like to propose a new feature to PHP: The in Operator
Bob mentioned a few weeks ago he wants such an operator in PHP and today I
stumbled over

http://nikic.github.io/2012/07/27/How-to-add-new-syntactic-features-to-PHP.html
again,
which uses the in operator as a sample.

I am very familiar with the in operator. However, the implementation
would be incomplete without handling loops via the in operator. Many
people when seeing an in operator also think of JavaScript. In that case
the in operator iterates over properties. As such in PHP we should be able
to iterate over associative arrays should the syntax be added.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in

Use cases:

$obj = new StdClass;
$obj->prop = "value";
$languages = ["PHP", "C", "Java"];
var_dump("PHP" in $languages); // true
var_dump("Python" in $languages); // false
var_dump(0 in $languages); // false
var_dump("0x0" in ["0e3"]); // false
var_dump("prop" in $obj); // true
var_dump("foo" in $obj); // false
var_dump("Hello" in "Hello World!"); // true

For strings, it would replace strpos("Hello World!", "Hello") !== false),
for arrays it would replace in_array($needle, $haystack, true)
and for objects it would be a replacement of property_exists($class,
$property)`.

This change would mainly be syntax sugar, but I think it's worth because:

• "0x0" in ["0e3"] would return false while in_array("0x0", ["0e3"])
  returns true, that's probably an edge case, but there may be a lot of
  people that don't use the $strict parameter, see http://3v4l.org/0K7E5
• It would solve the issue that it's hard to remember the order of the
  arguments for in_array and strpos, just had to look it up again.

I do think that it would be nice for a few different reasons but the in
operator as such can also cause a bit of confusion and misdirection
depending on how it is implemented. In the use cases above you do mention
some inconsistencies with PHP functions that already exist. Additionally
you did mention objects, in what scope would it properly leverage? My
assumption would be visible properties from the context which you are in.

Regards,

Mike

Hi Niklas,

I'd like to propose a new feature to PHP: The in Operator
Bob mentioned a few weeks ago he wants such an operator in PHP and today I
stumbled over

http://nikic.github.io/2012/07/27/How-to-add-new-syntactic-features-to-PHP.html
again,
which uses the in operator as a sample.

Use cases:

$obj = new StdClass;
$obj->prop = "value";
$languages = ["PHP", "C", "Java"];
var_dump("PHP" in $languages); // true
var_dump("Python" in $languages); // false
var_dump(0 in $languages); // false
var_dump("0x0" in ["0e3"]); // false
var_dump("prop" in $obj); // true
var_dump("foo" in $obj); // false
var_dump("Hello" in "Hello World!"); // true

For strings, it would replace strpos("Hello World!", "Hello") !== false),
for arrays it would replace in_array($needle, $haystack, true)
and for objects it would be a replacement of property_exists($class,
$property)`.

This change would mainly be syntax sugar, but I think it's worth because:

• "0x0" in ["0e3"] would return false while in_array("0x0", ["0e3"])
  returns true, that's probably an edge case, but there may be a lot of
  people that don't use the $strict parameter, see http://3v4l.org/0K7E5
• It would solve the issue that it's hard to remember the order of the
  arguments for in_array and strpos, just had to look it up again.

Bob would volunteer to implement that feature.

I would like to reserve 'in' and 'out' for Design by Contract (DbC).
http://en.wikipedia.org/wiki/Design_by_contract

D language has in and out like

function foo() {
in {
// precondition
}
out {
// postcondition
}
{
// function body
}

Contract programing can be done only with assert or annotation.
However, it's much easier/readable with native language support.
Contract programming is proved to be fast/robust/secure.

in operator can be useful, but it's the same as in_array().
If we need strict type check, we may do

$ php -r 'var_dump(in_array("0x0", ["0e3"], TRUE));'
bool(false)

as you mentioned.

I would like to reserve 'in' for DbC rather than syntax sugar.

Regards,

--
Yasuo Ohgaki
yohgaki@ohgaki.net