명령 구분
it's perhaps not obvious to some, but the following code will cause a parse error! the ?> in //?> is not treated as commented text, this is a result of having to handle code on one line such as <?php echo 'something'; //comment ?>
<?php
if(1==1)
{
//?>
}
?>
i discovered this "anomally" when i commented out a line of code containing a regex which itself contained ?>, with the // style comment.
e.g. //preg_match('/^(?>c|b)at$/', 'cat', $matches);
will cause an error while commented! using /**/ style comments provides a solution. i don't know about # style comments, i don't ever personally use them.
주석
PHP는 'C', 'C++', Unix 쉘 형식(펄 형식)의 주석(comment)형태를 지원한다. 예를 들면:
<?php
echo 'This is a test'; // 한줄짜리 c++ 스타일 주석
/* 여러줄의 주석
이줄까지 주석처리 된다 */
echo 'This is yet another test';
echo 'One Final Test'; # 쉘 형식의 한줄짜리 주석
?>
"한 줄" 주석 형식은 줄의 끝까지나 PHP 코드의 현재 블록까지 중, 먼저 오는 부분까지만 주석으로 처리합니다. 이는 // ... ?>나 # ... ?> 뒤에 오는 HTML 코드가 출력됨을 의미합니다: ?>는 PHP 모드를 종료하고 HTML 모드로 돌아가게 하므로, //나 #은 영향을 주지 않습니다. asp_tags 설정 지시어가 켜져 있으면, // %>나 # %>에도 동일하게 적용됩니다. 그러나, </script> 태그는 한 줄 주석에서 PHP 모드를 종료하지 않습니다.
<h1>This is an <?php # echo 'simple';?> example.</h1>
<p>The header above will say 'This is an example'.</p>
'C' 형식 주석은 첫 */에서 종료합니다. 그러므로 'C' 형식 주석을 중첩하지 않아야 합니다. 이는 큰 코드 블럭을 주석처리 하려고 할 경우에 자주 발생하는 실수입니다.
<?php
/*
echo 'This is a test'; /* 이 주석은 문제가 발생합니다 */
*/
?>
add a note
User Contributed Notes주석
theblazingangel at aol dot com
29-Aug-2007 07:55
29-Aug-2007 07:55
fun at nybbles dot com
14-Jul-2006 02:28
14-Jul-2006 02:28
a trick I have used in all languages to temporarily block out large sections (usually for test/debug/new-feature purposes), is to set (or define) a var at the top, and use that to conditionally comment the blocks; an added benefit over if(0) (samuli's comment from nov'05) is that u can have several versions or tests running at once, and u dont require cleanup later if u want to keep the blocks in: just reset the var.
personally, I use this more to conditionally include code for new feature testing, than to block it out,,,, but hey, to each their own :)
this is also the only safe way I know of to easily nest comments in any language, and great for multi-file use, if the conditional variables are placed in an include :)
for example, placed at top of file:
<?php $ver3 = TRUE;
$debug2 = FALSE;
?>
and then deeper inside the file:
<?php if ($ver3) {
print("This code is included since we are testing version 3");
}
?>
<?php if ($debug2) {
print("This code is 'commented' out");
}
?>
mst_NO_SPAM_TO_ME at mstsoft dot com
05-Jun-2006 09:38
05-Jun-2006 09:38
This "comment ends on line break or end of PHP Block" thing can be confusing. I discovered this by accident when working with XML Output from PHP...
<?PHP
header("Content-type: text/xml");
/*
echo "<?xml version=\"1.0\"?>";
echo "<page>multi-line comments work as expected.</page>";
*/
//echo "<?xml version=\"1.0\"?>";
//echo "<page>single-line comments end php mode and output your code.</page>";
?>
I would expect the comment to work, but there is no parsing in comments so the String suddenly becomes a PHP end-block tag, which is correct reading this documentation.
cheers,
martin
PS: You even see the behavior in the Syntax highlighting :-)
J Lee
26-May-2006 03:39
26-May-2006 03:39
MSpreij (8-May-2005) says /* .. */ overrides //
Anonymous (26-Jan-2006) says // overrides /* .. */
Actually, both are correct. Once a comment is opened, *everything* is ignored until the end of the comment (or the end of the php block) is reached.
Thus, if a comment is opened with:
// then /* and */ are "overridden" until after end-of-line
/* then // is "overridden" until after */
21-Jan-2006 06:46
M Spreij wrote, 08-May-2005 08:15...
A nice way to toggle the commenting of blocks of code can be done by mixing the two comment styles:
...
This works because a /* .. */ overrides //.
The final sentence should be the other way round, i.e.
This works because a // overrides /* .. */.
(If it didn't the /* .. */ would comment out the code regardless of whether an additional '/' is prefixed to the first line).
samuli dot karevaara at lamk dot fi
12-Nov-2005 01:30
12-Nov-2005 01:30
If you want to comment out large sections of code (temporarily, usually and hopefully), consider using
<?php
if (0) {
print("This code is 'commented' out");
}
?>
instead of /* comment block */. Otherwise, as noted here, you will have parse errors if the block that you commented out contains */ somewhere, like in regexp or in another comment.
hcderaad at wanadoo dot nl
30-Jun-2005 05:51
30-Jun-2005 05:51
Comments in PHP can be used for several purposes, a very interesting one being that you can generate API documentation directly from them by using PHPDocumentor (http://www.phpdoc.org/).
Therefor one has to use a JavaDoc-like comment syntax (conforms to the DocBook DTD), example:
<?php
/**
* The second * here opens the DocBook commentblock, which could later on<br>
* in your development cycle save you a lot of time by preventing you having to rewrite<br>
* major documentation parts to generate some usable form of documentation.
*/
?>
Some basic html-like formatting is supported with this (ie <br> tags) to create something of a layout.
M Spreij
09-May-2005 04:15
09-May-2005 04:15
A nice way to toggle the commenting of blocks of code can be done by mixing the two comment styles:
<?php
//*
if ($foo) {
echo $bar;
}
// */
sort($morecode);
?>
Now by taking out one / on the first line..
<?php
/*
if ($foo) {
echo $bar;
}
// */
sort($morecode);
?>
..the block is suddenly commented out.
This works because a /* .. */ overrides //. You can even "flip" two blocks, like this:
<?php
//*
if ($foo) {
echo $bar;
}
/*/
if ($bar) {
echo $foo;
}
// */
?>
vs
<?php
/*
if ($foo) {
echo $bar;
}
/*/
if ($bar) {
echo $foo;
}
// */
?>
Steve
15-Dec-2004 09:41
15-Dec-2004 09:41
Be careful when commenting out regular expressions.
E.g. the following causes a parser error.
I do prefer using # as regexp delimiter anyway so it won't hurt me ;-)
<?php
/*
$f->setPattern('/^\d.*/);
*/
?>