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To: Alice Wonder <alice@librelamp.com>, internals@lists.php.net
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Date: Mon, 18 Jun 2018 00:09:11 +0200
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Subject: Re: [PHP-DEV] [RFC][Under Discussion] Add functions array_key_first()
 and array_key_last()
From: enno.woortmann@web.de (Enno Woortmann)

Hi Alice,


Am 17.06.2018 um 22:16 schrieb Alice Wonder:
> boolean is a value, null is the absence of a value, which is more=20
> accurate, no?

In my opinion that's the argument to return null for either parameters=20
which aren't an array or empty arrays simply because a first/last key=20
isn't present and null is the value to be returned for an undefined state=
=2E
I've tested this behavior with other array_* functions which are=20
provided in the PHP core and they provide null consistently, eg.:

root@WOL-Soft-DEVVM:/var/www/WOL-Soft# php -r "var_dump(array_keys(1));"
PHP Warning:=C2=A0 array_keys() expects parameter 1 to be array, integer =

given in Command line code on line 1
NULL
root@WOL-Soft-DEVVM:/var/www/WOL-Soft# php -r=20
"var_dump(array_values('hello'));"
PHP Warning:=C2=A0 array_values() expects parameter 1 to be array, string=
=20
given in Command line code on line 1
NULL
root@WOL-Soft-DEVVM:/var/www/WOL-Soft# php -r "var_dump(array_flip(null))=
;"
PHP Warning:=C2=A0 array_flip() expects parameter 1 to be array, null giv=
en=20
in Command line code on line 1
NULL

There was another remark which wasn't sent to the internals mail list=20
but to my personal mail account (mehh :( ) which supported to return fals=
e:

"because a lot of functions act the way returning false when things go
wrong even when they normally only would return string/int/array which
should be justification enough: consistency"

An example for this argument was the function strpos which may be=20
checked with =3D=3D=3D or !=3D=3D against false.
But the real discussion about the return value and the facility of=20
comparison against another value is only interesting if we extend the=20
scope of this RFC to cover also array_value_(first|last), as null as an=20
array key is not supported and will be casted to an empty string. Due to =

this internal handling of array keys, null is for the functions=20
array_key(first|last) an unique return value to evaluate failures.

My opinion about this subject supports your argument as null is the=20
value which should be returned if the requested value is not defined. If =

a variable which is neither an array nor an array with entries is passed =

neither the first/last key nor the first/last value is a defined value=20
and thus null should be the return value.

Especially if we decide to extend the scope of this RFC to cover also=20
array_value_(first|last) there is no possibility to provide a return=20
value which doesn't collide with a possible array value. If cases occur=20
which may resolve into a collision, the usage of functions like=20
is_array() and empty()/count() is inevitable as both null and false are=20
valid values for an array value. To argument with the semantic of false=20
and null the correct return value should be null for each of the=20
proposed functions (as well the proposed functions which are currently=20
covered by the RFC as the extended version which also covers the methody =

array_value(first|last) ) as null defines an undefined value.

Regards,
Enno