Oddzielanie instrukcji
when the comment string contains '?>', you should be careful.
e.g. output code 1= code 2 is different with code 3
1. with //
<?php
// echo '<?php ?>';
?>
2. with #
<?php
// echo '<?php ?>';
?>
3. with /* */
<?php
/* echo '<?php ?>';*/
?>
Komentarze
PHP obsługuje komentarze w stylu 'C', 'C++' i powłoki Unix (styl Perl\'a). Na przykład:
<?php
echo 'To jest test'; // To jest jednoliniowy komentarz w stylu c++
/* To jest wieloliniowy komentarz
jeszcze inna linia komentarza */
echo 'To jest jeszcze jeden test';
echo 'Ostatni test'; # To jest jednoliniowy komentarz w stylu powłoki
?>
"Jednolinijkowy" styl komentarzy obowiązuje jedynie do konca linii lub bieżącego bloku kodu PHP, cokolwiek wystąpi pierwsze. Co oznacza, że kod HTML za // ... ?> lub # ... ?> ZOSTANIE wyświetlony: ?> przerywa tryb PHP i wraca do trybu HTML, i // lub # nie może wpłynąć na to. Jeśli, dyrektywa konfiguracyjna asp_tags jest włączona, to działa tak samo z // %> i # %>. Jednakże, znacznik </script> nie przerywa trybu PHP w jednolinijkowym komentarzu.
<h1>To jest <?php # echo 'prosty';?> przykład</h1>
<p>Nagłowek powyżej będzie mówił 'To jest przykład'.</p>
Komentarze w stylu 'C' kończą się na pierwszym napotkanym */. Upewnij się, że nie zagnieżdzasz komentarzy w stylu 'C'. Łatwo jest popełnić pomyłkę jeśli próbujesz odkomentować duży blok kodu.
<?php
/*
echo 'To jest test'; /* Ten komentarz będzie przyczyną problemów */
*/
?>
add a note
User Contributed Notes
Komentarze
team at researchbib dot com
13-Sep-2011 07:25
philip-php at dago dot yourweb dot de
05-Mar-2011 10:29
It's true, comments do not take up PROCESSING time, but they do take some PARSING time in case you are not using a compile cache of some kind.
jballard at natoga dot com
15-Dec-2010 02:28
Comments do NOT take up processing power.
So, for all the people who argue that comments are undesired because they take up processing power now have no reason to comment ;)
<?php
// Control
echo microtime(), "<br />"; // 0.25163600 1292450508
echo microtime(), "<br />"; // 0.25186000 1292450508
// Test
echo microtime(), "<br />"; // 0.25189700 1292450508
# TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST
# .. Above comment repeated 18809 times ..
echo microtime(), "<br />"; // 0.25192100 1292450508
?>
They take up about the same amount of time (about meaning on a repeated testing, sometimes the difference between the control and the test was negative and sometimes positive).
benny at bennyborn dot de
08-Dec-2010 03:16
This regex should do the job when trying to parse comments
(\/\*(.*?)\*\/)|(^|\s+)\/\/(.*?)(\n|$)|(^|\s+)#(.*?)(\n|$)
Wolfsbay at ya dot ru
12-May-2010 02:10
If you are using editor with code highlight, it’s much easier to notice error like /* */ */.
theblazingangel at aol dot com
28-Aug-2007 03:55
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.
fun at nybbles dot com
13-Jul-2006 10:28
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 05:38
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
25-May-2006 11:39
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 01:46
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
11-Nov-2005 08:30
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
29-Jun-2005 01:51
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
08-May-2005 12:15
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 04:41
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.*/);
*/
?>