Use isset over array_key_exists

[gmponos]

if for whatever weird reason someone sets CURLOPT_POSTFIELDS sets it us null and you also enable strict types in php7 then strlen(null) will blow up

[dbu]

thanks for contributing @gmponos . i am afraid i am 👎 on this change. i think isset hides problems. for one, if $options is not defined at all, we silently not see the options. but also, when the user specified a function resp. fields but its null, maybe the user had a mistake where their variable was null instead of what it should have been. with the isset we silently ignore those issues, instead of throwing a proper exception telling that this makes no sense.

i am fine adding an exception if the post fields are not a string. for the callback, we could check is_callable

[dbu]

the problem i have with isset is that it hides programming errors, like when $options is mistyped or something.

also, to spin your idea further, somebody could set the option to 42 or some object, and then we still fail.

i would prefer to have a check inside the if that throws an InvalidArgumentException when !is_string.

[dbu]

we do not use the option here but only check for existence of the option. i'd not change this here.

we define this field as a function:

curl-client/src/Client.php

Line 293 in 2ae49a4

$options[CURLOPT_READFUNCTION] = function ($ch, $fd, $length) use ($body) {

i would be ok to add an is_callable check to throw an InvalidArgumentException if you want.

[gmponos]

Basically the goal of this PR was to keep the code behavior the same after adding a declare(strict_types=1).

Thinking this twice after your comments it might be better to leave things as they are and let php blow if it is null. Maybe then handling the Throwable somewhere centrally and convert it to any Exception might be better.