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Date: Mon, 28 Jul 2025 19:31:30 +0100
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Subject: Re: [PHP-DEV] [DISCUSSION] Adding the "is_integer_safe()" function
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From: imsop.php@rwec.co.uk ("Rowan Tommins [IMSoP]")

On 28/07/2025 16:32, Larry Garfield wrote:
> Even without the precision loss question, such a function would be very useful when parsing input data of unknown type (and thus is a string).  "Can I cast this string to an int to use with an int parameter without any loss" is currently not as simple as it ought to me.  Providing a single standardized function for that would be most welcome.
>
> The name is quite long though. 🙂


This is basically where I was going with "can_lossless_cast". The reason 
I went with a generic-like syntax is because it makes it exntendible to 
any representable type, without an ever-growing list of long names like 
"is_representable_as_int_or_float".

I also see it as part of a wider set of missing cast functions; for any 
value V and type T:

1. Is V of type T?
2. Can V be safely converted to T (for some definition of "safe")?
3. If V can safely be converted to T, give that result; otherwise, throw 
an Exception|Error
4. If V can safely be converted to T, give that result, else return null
5. If V can safely be converted to T, give that result, else return a 
default value of type T


Given (5), you can implement (2), (3), and (4), but not elegantly, 
particularly if null is a valid output, e.g.:

( cast<?int>($v, default: false) !== false ) ? cast<?int>($v, default: 
false) : throw new TypeError('Not null, and not castable to int');

vs

cast_or_throw<?int>($v)


I've got a half-drafted RFC around this, but stalled on a) naming; and 
b) what a "safe" cast means for different types. It seems like both 
problems have already come to light in this thread.


-- 
Rowan Tommins
[IMSoP]