[RFC] Loosening heredoc/nowdoc scanner View as Markdown

Hi Stas,

Hi!

I would like to propose a few changes to our heredoc / nowdoc scanner to make it less awkward to use inside other constructs.

https://wiki.php.net/rfc/heredoc-scanner-loosening

Let me know your thoughts :)

With this proposal, you will not be able to use the delimiter inside the
text at the beginning of the line, which is a BC break and may be a
problem for some code.

Yes, that’s also mentioned in the RFC; although it would happen more easily when restrictions are completely removed, there’s a slim chance it would happen with the limited set of valid terminators. That said, I would like to quote from the RFC itself:

[…] it should be noted that the developer is in complete control of choosing the name for their enclosures; it's important to choose an enclosure that doesn't occur naturally inside the quotation.

I'm not sure saving one variable assignment, at
the expense of making scripts less readable and breaking BC, is really
worth it. How often you need an array of heredocs or concatenate two
heredocs?

There’s no real objective measure with which I can answer such questions :)

The closest I could come to a rebuttal is if there’s no real need to make the syntax so restrictive, why not make it less restrictive?

How often it is a good idea, readability-wise?

--
Stanislav Malyshev, Software Architect
SugarCRM: http://www.sugarcrm.com/

If the syntax of heredocs/nowdocs is to be loosened, the biggest aspect I’d like to see addressed is indentation. I can certainly see how it would be nice to loosen the restrictions around the post-closing-token newline to allow easier use in places like array definitions, but, I’ve never run into that problem myself. I have, however, been annoyed by the indentation limitations, so much so that I could probably count with my fingers the number of times that I’ve used the construct in the couple million lines of PHP I’ve written — even though I want to use it about once a week. I just find the side-effect on code formatting, when used in a container structure (class, function, method, loop, whatever), to be more than I can handle. Look at this simple example from the docs to see what I mean:

http://php.net/manual/en/language.types.string.php#example-89

One of the key benefits of consistent indentation is that it allows very rapid visual navigation of code by nearly eliminating the need for reading until you’ve zoned in on the right section of code. To illustrate this very well, just try to visually identify the code structure in this old-school BASIC code:

http://www.atariarchives.org/basicgames/showpage.php?page=3

That this restriction warrants italicized text inside a pink warning box in the docs suggests both that lots of people bump into it and that it runs counter to the expectations of the language.

Now, perhaps I’ve not felt constrained by the newline restriction simply because I so rarely get to use the construct at all because of the indentation restriction. That’s actually probably the case. So that idea is important to address, but I think it’s pointless to address without also addressing indentation.

What if we could do something like this:

function foo() {
$string = <<<
THEEND
This is the document text. Any
whitespace appearing in a column
that’s before the starting token
is automatically ignored for all
lines.
THEEND;

A few particulars:

• If the starting token appears immediately adjacent to the <<< sequence, then parsing is done according to existing rules (perhaps with the changes in the RFC). This both maintains BC and avoids issues where more or less whitespace is ignored when, for example, the variable is renamed.

• Extending the original proposal, the closing token can be indented without concern. Align it with the starting token, with the assignment line, whatever.

• The closing token could not appear within the text.

I’ve not given this solution deep thought, so I’m sure there are problems I’m missing. But if there’s a good solution to the indentation restrictions, I think it would be a huge win. And with the AST-based parser, there may be solutions that are possible now that were previously impossible, which makes this a good time to reconsider the problem.

--
Bob Williams
SVP, Software Development
Newtek Business Services, Inc.
“The Small Business Authority”
http://www.thesba.com/

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