Bug #48669: PHP now includes GOTO

http://bugs.php.net/bug.php?id=48669

by roder • 17 years ago

109 59 17 years ago

bugs.php.net

I'll admit, I loled.

What is the reasoning behind goto in PHP though? I know php well enough, and I can't think of a time or place I've ever said: "I really wish I had a goto here!"

roder• 17 years ago

Seems like a legitimate bug submission to me.

wvenable• 17 years ago

PHP is ubiquitous, and now I can be more easily targeted by languages that can compile to PHP. They must have had a use-case in mind when adding it, because it's a lot of work for nothing otherwise.

mnemonicsloth• 17 years ago

The standard Acceptable Goto is used to throw control between levels of a multiply-nested loop.

See also: call/cc for managing control flow in a tangle of mutually recursive functions.

blasdel• 17 years ago

But it's not "a lot of work" to implement at all!

All of the standard 'structured programming' constructs (if, while, for, switch, etc.) are just wrappers around conditional jumps in nearly every imperative language. switch even uses labels for fuck's sake!

reduxredacted• 17 years ago

If you've ever been able to think of a time or a place that you've said "I really wish I had a goto here!", it might be time for a rewrite or a new job.

Though, admittedly, I don't think I've ever looked at a piece of code I've written that was more than six months old without thinking "who the hell did this and why did they want to torture me?"

scott_s2• 17 years ago

See http://news.ycombinator.com/item?id=650027

shiro2• 17 years ago

Goto is pretty handy if you're not writing in the language but writing a translator to the language instead. That is, when some corporate politics demand the product must be in PHP but you feel you start losing your mind writing in it... well, write in your favorite language and compile it to PHP!

mrshoe• 17 years ago

Commonly cited use cases include:

    1. Break out of nested loops.
    2. Jump to cleanup code at the end of a function instead of an early return.

I never use goto, but I think the usual knee jerk reaction to it is sometimes unwarranted.

daremon• 17 years ago

About (1), what's wrong with break? (it also accepts a level e.g. break 3)

tilly• 17 years ago

If you have them in your language the common better solutions to those use cases include:

1. Labeled loop control 2. Exceptions

PHP has #2 and a bad form of #1. In PHP you get to say how many loops to break out of, but not the name of the loop to go to. This makes code less self-documenting and can be fragile when editing code.

Other uses of goto for which substitutes are harder to find are to to make your language a more convenient compilation target, and when interacting with other control structures not under your control. These uses are VERY rare. In a decade of professional Perl programming I have seen each used twice. None of the examples were in any code base I worked with. Two were in the Perl core, the first is that the s2p utility emits gotos to emulate branches in sed, and the second is that the original Switch.pm used a goto to break out of any loops that it happened to interact with. (That one was a computed goto! After all he didn't know how this switch might interact with other switches.)

I would be willing to use goto for nested loops in PHP, but only because PHP does not offer labeled loop control. While I like to believe that I understand when to use goto for other reasons, I doubt I'll ever encounter a serious need to do that in any language.

xtho• 17 years ago

There are better alternvatives for that:

  1. Many other languages use catch/throw or a more sophisticated version of break.
  2. This is often done with try/finally in other languages.

There is no excuse for re-introducing the goto command.

jacquesm• 17 years ago

Finally, it is now possible to produce true spaghetti code in PHP.

I wonder why this took so long. To this date the oversight of omitting goto from a language that otherwise seemed so geared towards obfuscation puzzled me greatly.

shaunxcode• 17 years ago

On the flipside it certainly makes implementing TCO a lot more possible for those of us generating php.

nir• 17 years ago

So, to summarize, it's useful for people building certain projects with PHP and at the same time a great boon for people making sarcastic comments about PHP. Win win.

elcron• 17 years ago

10 Yes,

20 COMEFROM 50

30 but when will they include comefrom.

40 COMEFROM 10

50 I always wanted goto,

60 COMEFROM 30

70 http://en.wikipedia.org/wiki/COMEFROM

gdee2• 17 years ago

a comefrom would indeed be interesting and arguably more useful...

commiebob• 17 years ago

http://xkcd.com/292/

mixmax• 17 years ago

I must be psychic, I just knew that link would show up in the comments.

Scriptor• 17 years ago

But the top one?

zackattack• 17 years ago

You're not psychic, you've honed your sense of prediction w/r/t your intelligence.

gchucky• 17 years ago

For some reason, the PHP documentation for goto has a link to that comic too. http://www.php.net/manual/en/control-structures.goto.php

jdale27• 17 years ago

"Gotos aren't damnable to begin with. If you aren't smart enough to distinguish what's bad about some gotos from all gotos, goto hell."

-- Erik Naggum, http://groups.google.com/group/comp.lang.lisp/msg/bb32931876...

TimMontague• 17 years ago

A few years back, Linus and some kernel hackers had a good discussion about the good gotos vs. the bad gotos.

http://kerneltrap.org/node/553

rjprins• 17 years ago

Every function call is a goto.

vegashacker• 17 years ago

Don't miss the

  goto hell;

at the bottom. Awesome.

ashleyw• 17 years ago

Wait, wait, wait...GOTO in PHP is real?? I thought it was a joke when I heard about it a while back...

Those who use PHP properly don't need this, and the ones who currently write spaghetti....well, will now write even worse spaghetti! At least the good developers now have another way to spot bad code, I guess..

humbledrone• 17 years ago

I was under the impression that the addition of "goto" was a joke. Are people actually using it? While there are legitimate uses for "goto," they are pretty much isolated to low-level C code, and are made unnecessary in a language that supports exceptions...

huhtenberg• 17 years ago

Exceptions vs. goto-based cleanup is purely a matter of personal programming taste and habits. Gotos exist because there are people who find them convenient, and not because gotos are "legitimate" in the context of that particular programming language.

Making the language minimalistic is never a goal of a language design unless it's a Brainfuck. If it were a goal, there would've not been three loop constructs in any modern languages.

silentOpen• 17 years ago

http://barker.linguistics.fas.nyu.edu/Stuff/Iota/

eru3• 17 years ago

Scheme does not have _any_ loop constructs. Neither does Haskell. (Apart from the standard library. There you find some `simulators' of loops.)

ivanstojic• 17 years ago

Next up, PHP 6 will include ComeFrom.

kwantam• 17 years ago

comefrom is an excellent and seriously useful instruction.

My team has (kind of) implemented it in hardware as a way of patching ROM code in RAM. When the PC becomes equal to an address in the comefrom table, the PC is loaded with a RAM address and execution continues there.

If you have a big chunk of code that could need small tweaks, storing it in ROM and implementing a small RAM alongside it saves a lot of chip area.

I'm almost 100% sure Freescale does this on some of their 32-bit microcontrollers.

Yes, I design ICs. No, I do not work for Freescale.

snorkel• 17 years ago

"why turn the language into a public menace?"

Too late.

vlucas• 17 years ago

I am an avid PHP developer, and I can't believe this actually did get added into PHP5.3. Even when I was a total noob I never wished the language had a 'goto' feature. I don't understand why this needs to be in a scripting language.

I guess now it will be even easier to spot bad PHP code. That's the only plus I can think of.

hvs• 17 years ago

It's usually pretty easy to spot bad PHP code anyway. Just open it in a text editor.

edw519• 17 years ago

  Goto floor(10);
  window.open();
  jump();

caillou• 17 years ago

you are aware that PHP uses -> rather than . to access an object method? ;)

Legion• 17 years ago

It's kind of chuckle-worthy because it's being added in so late in the game, and because of the smart-ass bug report, but this is a non-issue.

In saying this, I take my life into my own hands, as you can now bet that I will be forced in the future to work on fixing some code written by someone that takes this new feature and runs with it.

bartl• 17 years ago

The label, is that global? The docs say:

> This is not a full unrestricted goto. The target label must be within the same file and context, meaning that you cannot jump out of a function or method, nor can you jump into one.

but that doesn't quite imply that the label names don't need to be unique.

That would be quite typical for PHP, IMHO, with its global scope of top level variables (= not in a function) of old.

mildweed• 17 years ago

Previous thread: http://news.ycombinator.com/item?id=649507

dunk010• 17 years ago

I can understand the use as a labeled jump for loops, that's handy. Are there other cases where this is useful? I'm thinking along the lines of things like Quercus.

dmoney• 17 years ago

When you're writing something that's modeled as a state machine, it's easier to use goto to jump between the states, rather than simulating it with a while loop, state variable, and case statement. Making the program's behavior conform to a flow chart would probably be about the same.

I wonder: would goto have a better reputation if flowcharts were used more often?

uninverted• 17 years ago

I bet a lot of Basic code can be compiled to PHP just by changing the caps.

eru3• 17 years ago

And colons to semicolons. (Does Basic still use them to separate statements on the same line?)

RyanMcGreal• 17 years ago

[4 Aug 6:47pm UTC] andrei@php.net

Win.

voidpointer• 17 years ago

If there was any doubt left that PHP is the VisualBasic of the web it should be cleared now.

BTW, I think nobody linked the classic goto critique from Dijkstra yet: http://www.cs.utexas.edu/~EWD/transcriptions/EWD02xx/EWD215.... (or paywalled in ACM context at http://portal.acm.org/citation.cfm?id=362929.362947 )

Dijkstra was pretty specific about the cases where goto would be confusing and made a case that one should would be better off just not using it at all. His argument applies much more to gotos that can jump across procedure boudaries. Most surviving gotos (including the PHP goto) are not that unconstrained so they do represent a compromise between Dijkstra's position and the pragmatic use of goto where it actually improves the readability of code - especially when exceptions are not available for some reason.

KevBurnsJr• 17 years ago

That's pretty funny. But 5.3 did also come with lambdas, anonymous functions, closures and namespaces. http://www.recessframework.org/page/map-reduce-anonymous-fun...

extension• 17 years ago

Control structures are high level abstractions around common patterns found with jumps and conditional branches. Many such patterns have been identified, ranging in complexity from simple loops and conditionals to non-local returns to cooperative multi-threading.

To assert that there is no possible good use for GOTO implies that every conceivable control flow pattern has a more clean and intuitive implementation using only the high level control structures.

When you consider the variation, from language to language, in the selection of control structures available, the conjecture seems absurd. At the very least, GOTO is a reasonable compromise when forced to use a language like C, which lacks structures for such common patterns as exceptions, among others.

What is certainly worse than using GOTO is contorting code to use high level control structures in counter-intuitive ways, or worse yet, implementing ad-hoc control mechanisms using conditional variables. For purposes of readability, an informatively labeled GOTO is greatly preferable to such obfuscation.

Fortunately, we have versatile languages like LISP and Ruby which provide a rich library of control flow abstractions and allow us to create our own using closures. For the rest of the world, let them have their GOTO.

Bug #48669: PHP now includes GOTO

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