[Docs] Improve `openssl_x509_verify()` to indicate that the return value is dangerous

[TimWolla]

Affected page

https://www.php.net/manual/en/function.openssl-x509-verify.php

Current issue

Returns 1 if the signature is correct, 0 if it is incorrect, and -1 on error.

This means that both the success case and the error cases are truthy, which makes code like:

if (openssl_x509_verify()) { … }

dangerous.

Suggested improvement

A warning should be added to always compare === 1. The code example should be updated to === 1 instead of == 1 as well.

Additional context

Same applies to openssl_verify() and possibly others.