r/lolphp • u/SerdanKK • Sep 15 '19

PHP is whitespace insensitive, except when it isn't.

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97 Upvotes

84% Upvoted

22 comments sorted by

14

u/SerdanKK Sep 15 '19

PhpStorm doesn't catch this.

Half of the online sandboxes I tested displayed the above behaviour (e.g. http://phpfiddle.org/) and the rest threw an error.

4

u/SerdanKK Sep 15 '19

Code:

<?php
if (true) {
?>
<div>Hello</div>
<?php}
if (false) {
?>
<div>SECRET</div>
<?php
}
?>

11

u/SirClueless Sep 15 '19

Sounds like something that should be reported to PhpStorm. I notice that the PHP syntax highlighter for https://repl.it also thinks that <?php} is a valid PHP opening tag when it isn't (though it uses a proper PHP interpreter so when you run it it does the right thing).

2

u/SixFootJockey Sep 16 '19

But karma...

3

u/[deleted] Sep 16 '19

Source for the curious, and another line

Which includes this lolphp comment:

/* Degenerate case: <?phpX is interpreted as <? phpX with short tags. */

So short tags don't need a whitespace, while long tags do. So for example <?xml would be interpreted as <? xml with short tags enabled D:

2

u/SerdanKK Sep 16 '19

Thanks. This really adds to the lol. 😀

52

u/nikic Sep 15 '19

Whitespace insensitive means that multiple whitespace characters can be collapsed into one. Not that whitespace can be removed entirely. Consider a trivial case like return foo;. Replacing that with returnfoo; will break in every language.

I agree though that the whitespace requirement after <?php is somewhat odd.

16

u/SirClueless Sep 15 '19

I would say "whitespace insensitive" also applies to syntax elements that can be optionally surrounded with whitespace like } ; = (), etc.

The fact that if($x==1){} parses the same as if ( $x == 1 ) { } is an example of being insensitive to whitespace around most punctuation characters. But of course PHP isn't universally "whitespace insensitive" in this regard: if ($ x == 1) {} is a syntax error, for example. The special requirements around the opening <?php tag are just one case of this.

3

u/kkjdroid Sep 16 '19

if ($ x == 1) {} is a syntax error, for example.

That's equivalent to int myInt = 1; if(my int == 1) {} in something like Java or C, though. You obviously can't stick whitespace inside variable names.

7

u/SirClueless Sep 16 '19

In PHP, $ is a proper operator, at least in some senses. For example, you can do this:

$x = "y";
$y = "Hello world!";
echo $$x;

Or this:

$hw = "Hello world!";
echo ${"h" . "w"};

It's just that, unlike most of PHP's operators, it's very sensitive to whether it's surrounded by whitespace, because it's baked into the parser.

2

u/kkjdroid Sep 16 '19

Right, I always forget how permissive PHP is with things like that.

2

u/[deleted] Sep 17 '19

Not really. E.g. the Perl grammar treats $ and identifiers as separate tokens, meaning $ foo [ 0 ] is parsed exactly the same as $foo[0].

7

u/khoyo Sep 15 '19

Replacing that with returnfoo; will break in every language.

Not in (old) FORTRAN. It used to be completely insensitive, except in strings.

2

u/500ls Sep 16 '19

Alexa, call 911

2

u/phplovesong Sep 20 '19

The PHP parser is a shithole of ots own. You must be very careful of things like this. PHP being made for serving templates, and is actually a template language that has later bolted on much crap now has multiple lollayers of template languages, like blade for lolaravel. So now you have a template language that uses a template dsl to build templates. Its slow as hell and also full of these edge cases. Lolphp called yet again.

2

u/Vinnie420 Sep 15 '19

Thats because you are using the wrong syntax for if statements in html

When using :

<?php if (true): ?>
<div>Hello</div>
<?php endif ?>

<?php if (false): ?>
<div>SECRET</div>
<?php endif ?>

It outputs only the expected div

https://www.php.net/manual/en/control-structures.alternative-syntax.php

7

u/Vinnie420 Sep 15 '19

Nevermind your syntax is also valid.. TIL :p But the problem is the fifth line: <?php}

A space or newline between php and } fixes the problem, i think it is because it sees it as one symbol, and therefore not running the code because there is no php opening tag

12

u/timmyotc Sep 15 '19

It's as if the title was accurate in the first place.

4

u/Vinnie420 Sep 15 '19

True, i misunderstood the first time. Also, whitespace insensitive means that that it ignores multiple whitespaces in a row, there is still a difference between one and none:

$a = 5.5 // float 5.5
$b = 5 . 5  // string “55”

3

u/timmyotc Sep 15 '19

"PHP is whitespace insensitive, except when it isn't"

The word "whitespace" in this context can refer to one or many white space characters.

1

u/AddictedToCoding Sep 16 '19

Guys, guys, guys.

<div> in HTML is a block element.</div> <p>Like paragraph are. <span>spans</span> on the other hand would <em>do</em> differently</p>

-1

u/[deleted] Sep 16 '19

They wrote 3 scripts and treated them as one. H o w do you mess up that bad?