On Sat, Feb 27, 2021 at 3:00 PM Rowan Tommins <rowan.coll...@gmail.com> wrote:
> Hi all, > > I would like to propose we formally deprecate the function debug_zval_dump > and remove it in PHP 9.0. > > This function is mostly similar to var_dump, with the additional ability > to output the refcount of a variable. This has always been hard to > interpret, but is now so complex as to be effectively useless: > > - Because it is implemented as a function taking a parameter in the normal > way, the refcount has been modified by the time it is displayed. Depending > on the value passed, this may include reference separation; in older > versions of PHP, it was possible to affect this directly by forcing a > pass-by-reference. The manual still discusses this, but it hasn't been > possible since PHP 5.4. [1] > - Since PHP 7, some types don't have a refcount at all, and references are > represented by additional levels of zval. Without completely changing the > output format, this information is impossible to convey accurately. > - Optimisations affect the refcount in increasingly non-obvious ways. For > instance, an array defined literally in the source code has an extra > counted reference compared to one which has been modified at runtime. [2] > > Since this is a rather specialised piece of debugging information, not > useful to the average user, I think it should be left to dedicated > debugging tools. XDebug includes an equivalent function that takes a name > and looks it up in the symbol table, avoiding some of the worst issues [3]. > I'm not familiar with PHPDBG, and it doesn't seem to have much > documentation, but I assume it would be able to display this as well. > > I notice there's a draft for an omnibus "deprecations for PHP 8.1" RFC > [4]. Should I add this there, or raise a separate RFC? > > Refs: > 1: https://www.php.net/debug-zval-dump > 2: https://3v4l.org/DVi3f > 3: https://xdebug.org/docs/all_functions#xdebug_debug_zval > 4: https://wiki.php.net/rfc/deprecations_php_8_1 > > Regards, > -- > Rowan Tommins > [IMSoP] Can't say I've had much use for debug_zval_dump(), but I don't really see the motivation for removing it either. For PHP 8.1, I have already adjusted it to dump "interned" instead of a refcount for interned strings and immutable arrays. If we additionally change it to explicitly print reference wrappers, I believe that debug_zval_dump() will produce a faithful representation. Regards, Nikita
