50

If I wanted to write a really long variable name like:

$this_is_my_variable_that_does_something_in_the_following_function_and_provides_some_information_with_which_the_function_relies_upon_to_do_all_the_work_it_needs = null;

would that work? same question for function/method names

james
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    You should make that camel case, otherwise it is hard to read. – Parris Varney Dec 30 '10 at 20:04
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    @PMV: `$thisIsMyVariableThatDoesSomethingInTheFollowingFunctionAndProvidesSomeInformationWith WhichTheFunctionReliesUponToDoAllTheWorkItNeeds = null;` Yeah, that looks easy to read. I can say it in a single breath! **\*inhales\*** – BoltClock Dec 30 '10 at 20:05
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    @BoltClock: Probably capitalize NULL too, since it's a constant. Then it would be a perfectly readable and sensible statement. Too bad punctuation isn't allowed though. – Parris Varney Dec 30 '10 at 20:08
  • @PMV: Yeah I forgot that. I always capitalize it in my code. – BoltClock Dec 30 '10 at 20:13
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    A good question, but trivial to answer for yourself. Did you try it? – HappyDog Sep 16 '19 at 11:10
  • As PHP doesn't define any limit. I do prefer ANSI standards, it recognizes a length of 31 characters for a variable name. However, the length should not be normally more than any combination of eight alphabets, digits, and underscores. – Amitesh Bharti Dec 16 '21 at 07:11

6 Answers6

246

Generally, such a limit is imposed by the threat of violence from other folks who interact with your code.

ceejayoz
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    I just had a good laugh reading your explanation. The exact same thing often happens if your code only uses only single-letter variables like `$i`, `$n` or `$k`. – Jocelyn Dec 01 '12 at 02:44
  • So, `if (strlen($varname) < 4 || strlen($varname) > 16) { SKINNERRRRRR(!!!!!1); }` – thomasrutter Jan 14 '14 at 14:16
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    @RobinJ By choice of the posting user, like every other accepted answer on the site. It's also, IMO, a perfectly accurate answer - technological limitations aren't the only ones. Also, it's five years old... why ask now? – ceejayoz Apr 10 '15 at 16:56
99

From the documentation:

Variable names follow the same rules as other labels in PHP. A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores

The same is the case for function names, as stated here.

Jeff Puckett
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Klaus Byskov Pedersen
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  • So writing 200 underscores on a line (and a semicolon at the end) is perfectly valid as long as notices are switched off! Time to introduce my new separators :) – dkellner Nov 23 '18 at 15:10
  • I would prefer the ANSI recommendation for the safer side given for C after all PHP is written in c (a length of mo more than 31 characters for a variable name.) – Amitesh Bharti Dec 16 '21 at 07:13
18

The limit in variable/function/method/class name length does not exist.

Comments above states that that this property should not be exploited. That is true only when it comes to human readable/human maintainable code.

However, this is extremely useful feature of PHP, that is exploited very well in a lot of very popular projects, such as Twig per example, which generates classes, example (a snippet):

class __TwigTemplate_9601167421099bbb502d119e674fed3fb71769eef256903648c9c2b4b6faa436 extends \Twig_Template {

    protected function doDisplay(array $context, array $blocks = array())
    {
        $__internal_0abebc74dd811fd7b4cfa4c6a2fdf870d7723c04e8daf6926b04914d6644935f = $this->env->getExtension("native_profiler");    
    }

}

I had opportunity to benefit from same property as well in my projects.

In conclusion:

  • There is no limit in var/func/class name length
  • It is extremely useful language feature
  • There is a context for its usage, of course, it is not for every day work
Nikola Svitlica
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3

There is no limit - but it is highly not suggested as it creates unreadable code...

zsalzbank
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    All the opposite, it does create very readable code indeed. It's much more expressive `$arrivalDateTimeWithUnknownTimeZoneAndIncorrectlyAssignedUtcTimeZone` (real example from our production code) than just `$arrivalDateTime`. Reason: In the second one the human reading your code will have to ask you if there's a bug or not because it has an Utc time zone while in reality the time zone was actually unknown. In the first case it's clear it was on purpose. – Xavi Montero Jul 07 '18 at 23:28
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    It makes very unreadable code and makes the code harder to type. There's a reason why comments exist, don't put all the information in the variable name. – brianush1 Jul 12 '18 at 17:33
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    On the other hand, comments are harder to maintain. When you have the reason for a variable on it's own name, it makes life easier. It actually takes less time to read a long variable, than always having to go to the definition and reading a comment. – Mateus Viccari Jul 26 '19 at 17:33
  • Big variable/function/etc names run the risk of misspelling; forget a double-r or a capital-Z on `$arrivalDateTimeWithUnknownTimeZoneAndIncorrectlyAssignedUtcTimeZone` and try to find the error on a heavy coding day. If you need to travel such a variable across hundreds of lines of code I would suggest describing it by code, like: `$arrivalDateTime = array("timestamp" => 3213546, "timeZone" => false, "assignedUTC" => false);` – Geo Halkiadakis Nov 22 '19 at 18:11
3

PHP does not pose a length limit on it's identifiers.

That said, I'm not sure why anybody would ever want to create a 160 character variable name. I hope this is a hypothetical question.

Craige
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    Well I was thinking of writing of framework/coding standard that didn't use comments and instead relied on using really descriptive variable and function names =P – james Dec 30 '10 at 20:03
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    You should name it Framework/CodingStandardThatDoesn'tUseCommentsandInsteadReliesonUsingReallyDescriptiveVariableandFunctionNamesCMS. – ceejayoz Dec 30 '10 at 20:08
  • Ugh. So you expect a long variable name to substitute for a comment that explains why someone did something bizarre? Good luck with that. – Brian Clapper Dec 30 '10 at 20:09
  • Maybe it's just dynamic stuff identifiers ;) – Thiago Macedo May 26 '14 at 15:51
  • There is a usage context - auto generated vars/classes/functions – Nikola Svitlica Sep 14 '15 at 09:26
  • Not 160, but this is real production code for me: `$arrivalDateTimeWithUnknownTimeZoneAndIncorrectlyAssignedUtcTimeZone`. +1 for @ceejayoz and clean code rulez! – Xavi Montero Jul 07 '18 at 22:29
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PHP doesn't have any restriction for variable name. And my suggestion is that variable name must consist the definition of the data which you are gonna store into it.

Rupesh Ranjan
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    You answered a question almost 9 years later, with adding no new points. Please consider answering an old question only if you can provide a different solution/answer. – MAChitgarha Jul 24 '20 at 13:46