Req #24750 [Opn->Csd]: Heredoc-Syntax
Edit report at http://bugs.php.net/bug.php?id=24750&edit=1
ID: 24750
Updated by: jani@php.net
Reported by: ssilk at fidion dot de
Summary: Heredoc-Syntax
-Status: Open
+Status: Closed
Type: Feature/Change Request
-Package: Feature/Change Request
+Package: Scripting Engine problem
PHP Version: Irrelevant
-Assigned To:
+Assigned To: jani
Block user comment: N
Private report: N
Previous Comments:
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[2009-11-19 11:48:37] RQuadling at GMail dot com
This bug has been fixed.
<?php
echo <<< END_HEREDOC_WITH_A_TRAILING_SPACE
1
2
3
END_HEREDOC_WITH_A_TRAILING_SPACE;
echo 1 / 0;
outputs...
Parse error: parse error in ... on line 2
The trailing space triggers the parse error.
Removing the trailing space and the output is, as expected ...
1
2
3
Warning: Division by zero in ... on line 8
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[2003-07-22 08:37:03] ssilk at fidion dot de
In addition to above the arguments in the tag-like syntax be very useful
writing queries:
$hu="a string with singlequotes '<- here"
$go="More singlequotes '''''";
...query(<<<<sql strip_nl ignore_indent addslashes>
SELECT * FROM table
WHERE bla = '$hu' and blubb='$go'
</sql>);
Which should be obviously useful.
[An abbreviation for the above could be
...query(<<<<sql sqlquery>
SELECT * FROM table
WHERE bla = '$hu' and blubb='$go'
</sql sqlquery>);
or perhaps also
...query(<<<<sqlquery> ...</sqlquery>)
which makes this tag to a special tag.
For those who don't like inline vars in a query:
...query(<<<<sql some other arguments>
($hu, $go)
SELECT * FROM table
WHERE bla = '?' and blubb='?'
</sql sqlquery>);
Other guys are better in finding a useful syntax.
]
I can imagine many cases, where other arguments can change the behaviour
in some way that matches a special kind of API. For example regex/pcre,
urlencode, dates, printf, print_r etc. Can be extended nicely and upward
compatible to the needs we have.
Inflation of features is a thing which must be carefuly watched.
Another aspect is, that documentation of some functions are easier. Take
for example preg_match():
Current:
preg_match('/\\\\\?/',$var);
// match '\?' - nearyl unreadable and hardly to understand
With tagged quoting:
preg_match(<<<<pcre>/\\?/</pcre>,$var);
// much more readable :-)
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[2003-07-22 07:03:50] ssilk at fidion dot de
Description:
------------
I read the bug #13610 and other depending stuff and I think the core of
the problem is, that heredoc-syntax is some kind of confusing, because
of the sensitivity for whitespace-characters (Space, Tab, CR, LF...)
(and perhaps the fixating for the OS-newline-character).
Here are some examples of realy time-consuming error-searches:
// example #1
echo <<<heredoc
There is a SPACE between
the identifier and the end of line;
PHP thinks now, the identifier is
"heredoc " (with space at the end)
and not "heredoc" as assumend.
heredoc;
// fails, instead PHP thinks
// it is still inside the heredoc
// so it prints out very funny error messages.
//
// Here is a tip for the documentation:
//
// This case could be tested easily if you type something
// looking like a "array-var" like $a['b']
// If PHP says there is an error in the line above
// then you have the "whitespace-identifier-problem".
// (the ' is important here! Perhaps there are some
// other testcases)
// example #2
echo <<<heredoc
Now we made all right above, but
for more readable code we added a space
before the semicolon at the end:
heredoc ;
// same problem as above, but the other way around. :)
This problem is not very obvious to even experienced programmers.
So currently a developer must try to avoid any whitespaces in
conjunction with heredoc-identifiers!
I suggest here (see bug #5804 at the end, feature request by Hartmut) to
change the parser to stop parsing the identifier if it finds a
whitespace. I think this avoids many problems with it and I think the
current implementation provokes missinterpretation.
Perhaps - to enable more complicated stuff - adding a new heredoc-syntax
like
echo <<<<tag-like-syntax...>This is a tag-like syntax...
The end of the string
is marked with <\/tag-like syntax...>
(the above \\/-escape sequence
must be added to this routine).
The end can exist in the same line
and not only at the
begin of a line</tag-like-syntax...> ; // end of string
Think, this kind of heredoc is very "readable", cause every PHP-user
knows what a tag is and how it works. This also comes into some
direction to Pearl (the ugly q-syntax, I realy hate it :), but this is
some more nicer.
Perhaps some special ideas here. Just implementing tag-like strings, it
could be useful to also add arguments:
echo <<<<string ignore_indent=1 strip_nl>
This enables you to indent the string,
but in the output the indenting is stripped away.
Also it deletes the newlines at the begin and
end of the string.
</string>
Some more (very useful) arguments are thinkable.
A more intelligent error handling in cases, when inside a heredoc-string
an error occours, could also help a lot (printing out the found
identifier within quotes) or a error-message, that the awaited
identifier isn't valid or something like this kind.
All in all heredoc is very useful. See also the useful feature request
in Bug #8685 ('<<-'-syntax).
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