[#13998][Bug][PHP] Move isNullable section to the top of the setter function in templates

[MustansirS]

Resolves #13998

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[MustansirS]

@jebentier @dkarlovi @mandrean @jfastnacht @ybelenko @renepardon @wing328 This PR is ready for review

[wing328]

@MustansirS thanks for the PR. I notice that the check for optional field has been replaced by isNullable check instead.

Shall we keep the check for optional field?

[MustansirS]

I noticed that a null value will never be passed to the setter function if it is not a nullable field:

https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache#L516

And if we keep the check as the check for just the optional field, then the original problem of the issue will persist and an operation such as a preg_match on a null value will be attempted

[MustansirS]

@wing328

[wing328]

thanks for the explanation.

[wing328]

tests passed via https://app.travis-ci.com/github/OpenAPITools/openapi-generator/builds/257997016

[wing328]

thanks for the fix. lgtm but i've not tested it locally

let's give it a try to see if anyone has further feedback on this fix.

[MustansirS]

Thank you!