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Subject: Re: [RFC] Deprecations for PHP 7.1
From: ajf@ajf.me (Andrea Faulds)

Hi Nikita,

Nikita Popov wrote:
> This RFC is incomplete -- I'm posting it now so people can suggest other
> things that should be deprecated. I expect it to grow over time and don't
> plan to vote on it in the immediate future.

I think this would be a good opportunity to look at our existing php.ini 
directives, with view to getting rid of some more of them eventually.

Three in particular spring to mind:

* `precision` and `serialize_precision` - These determine how many 
digits are printed when outputting floating-point numbers.
   - `serialize_precision` is used when serialising or exporting 
numbers, and would seem to exist solely to allow you to shoot yourself 
in the foot, by discarding possibly important information when 
serialising - an operation that's supposed to perfectly reproduce a value!
   - `precision` is used in other contexts, and is more problematic, 
because its default value is 14 which is less than the maximum number of 
decimal digits in a PHP float. This means that, by default, PHP doesn't 
print floats to their full precision - including in var_dump(). This can 
create unreasonable confusion when debugging (why are two numbers that 
appear identical with var_dump() reported as inequal?), means 
potentially important information is removed by default, and really 
ought not to be a global setting anyway: if you want to format your 
numbers with reduced precision, do so explicitly.
   - Both of these are settings which code may implicitly depend on and 
break when they are changed. The manual is unhelpful here, because it 
doesn't warn you that `precision` is used when floats on any page except 
that for php.ini!
* `mbstring.func_overload` - This piece of magic replaces the standard 
string functions with their mb_* equivalents. It is the character 
encodings equivalent of magic quotes: it simply assumes that all string 
operations on binary strings, if replaced by "multi-byte" versions, will 
suddenly handle character encodings properly. They won't necessarily, so 
this is quite a reckless setting. Worse, this setting prevents you from 
using the normal, non-"multi-byte" string functions when you need them 
for binary data, so PHP packages which deal with binary data are broken 
when this php.ini setting is turned on. Luckily, apps which rely on this 
setting being on could be easily fixed: by using find/replace.

There might be others worth dealing with, too, these are just the first 
three I thought of.

Thanks.

-- 
Andrea Faulds
https://ajf.me/