PHP 8.0 polyfill compatibility

[Ion Bazan]

I'm opening this issue to discuss the ways we could assure compatibility of symfony/polyfill-php80 with PHP versions < 7.0.
The only reason we require PHP >= 7.0 for this polyfill is fdiv() function that I found impossible to port to older versions and recently added type hints. However, all other features we polyfilled so far:

• Stringable interface
• ValueError class
• FILTER_VALIDATE_BOOL constant
• preg_last_error_msg function
• str_contains function
• get_debug_type function

would work just fine on PHP 5.3+! Maybe it would be worth considering enabling support for older versions of PHP and just conditionally disabling fdiv polyfill on older versions. I know it would add an extra condition in bootstrap.php but we should decide if we want more compatibility or more consistency of polyfilled features.

[Nicolas Grekas]

We can split the class in two Php80 and Php80Fdiv. Up for a PR?

[Nicolas Grekas]

But we could also let things as is. PHP 5 is getting old, why spend time on it now?

[Graham Campbell]

Do we wanna polyfill https://wiki.php.net/rfc/token_as_object too (assuming it is accepted).

[Nicolas Grekas]

Only if one needs it, so it should come by demand IMHO, not by anticipation. And the one demanding should be the implementer ideally also.

[Adam Charron]

What about str_starts_with and str_ends_with? Looks like these were added as well.

https://php.watch/versions/8.0/str_starts_with-str_ends_with

[Nicolas Grekas]

@charrondev check #250

[Laurent Laville]

@GrahamCampbell to follow your comment, I agree with you, and until it will include in polyfill-php80, an alternative exists at https://github.com/PHPWatch/phptoken-polyfill

[Tyson Andre]

There's also class Attribute - I didn't see any issues or PRs mentioning this.

E.g. in this example snippet, it would throw an Error in php 7 and older if there was no definition for Attribute

<?php

// This line crashes without a polyfill for Attribute.
const FUNCTIONLIKE_ATTRIBUTES = Attribute::TARGET_FUNCTION | Attribute::TARGET_METHOD; 

#[Attribute(FUNCTIONLIKE_ATTRIBUTES)]
function example() {
}

More broadly, in code which extracts attributes (e.g. from the tokenization in php 7 converting T_COMMENT to attributes), or in code which optionally supports attributes, it would also be useful to have a polyfill of attributes.

E.g. statically checking if an class could be a repeatable attribute, you'd need to know Attribute::TARGET_ATTRIBUTE.
(Context: I'm currently working on attribute static analysis support for https://github.com/phan/phan/ v4)

• It's easy enough for an application to add its own polyfill/workarounds, and this is a rare use case, so I don't have strong opinions of whether it's required.
• There's also the possibility that more class constants would get added to Attribute later. I guess any polyfill could just use the newest php 8.x version's functionality and be backwards compatible.

An reference polyfill to match php 8.0 would be

<?php

// EDIT: Attribute would have #[Attribute] to indicate that it is an attribute
#[Attribute(Attribute::TARGET_CLASS)]
final class Attribute {
    const TARGET_CLASS = 1;
    const TARGET_FUNCTION = 2;
    const TARGET_METHOD = 4;
    const TARGET_PROPERTY = 8;
    const TARGET_CLASS_CONSTANT = 16;
    const TARGET_PARAMETER = 32;
    const TARGET_ALL = 63;
    const IS_REPEATABLE = 64;

    /** @var int */
    public $flags;

    public function __construct(int $flags = Attribute::TARGET_ALL) {
        $this->flags = $flags;
    }
}

[Nicolas Grekas]

That'd make sense, PR welcome!