Basis syntax
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.
Commentaar
PHP ondersteunt 'C', 'C++' en Unix shell stijl (Perl stijl) commentaar. Bijvoorbeeld:
<?php
echo 'Dit is een test'; // Dit is een c++ stijl commentaar van 1 regel
/* Dit is commentaar van meerdere regels
en weer een regel commentaar */
echo 'Dit is weer een test';
echo 'Een laatste test'; # Dit is een shell stijl commentaar van 1 regel
?>
De "één regel" commentaar stijlen voegen enkel commentaar toe tot het einde van de regel of het huidige blok PHP code, ongeacht welke als eerste komt. Dit betekent dat HTML code na // ... ?> of # ... ?> gewoon wordt getoond: ?> breekt uit de PHP modus en herstart de HTML modus, en // of # kunnen dat niet beïnvloeden. Als de asp_tags configuratie-instelling aan staat, zal deze zich hetzelfde gedragen bij // %> en # %>. Desalniettemin breekt de </script> tag niet uit PHP modus in een één regel commentaar.
<h1>Dit is een <?php # echo 'simpel';?> voorbeeld.</h1>
<p>De header hierboven zal 'Dit is een voorbeeld' zeggen.</p>
'C' stijl commentaar stopt bij de eerstvolgende */. Zorg ervoor dat je geen 'C' stijl commentaar in elkaar embed. Deze fout is snel gemaakt als je een groot stuk code om wil zetten in een blok commentaar.
<?php
/*
echo 'Dit is een test'; /* Dit commentaar zal een probleem veroorzaken */
*/
?>
add a note
User Contributed NotesCommentaar
theblazingangel at aol dot com
29-Aug-2007 12:55
29-Aug-2007 12:55
fun at nybbles dot com
14-Jul-2006 07:28
14-Jul-2006 07:28
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 02:38
05-Jun-2006 02:38
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 08:39
26-May-2006 08:39
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 10:46
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 05:30
11-Nov-2005 05:30
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 10:51
29-Jun-2005 10:51
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 09:15
08-May-2005 09:15
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 01:41
15-Dec-2004 01:41
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.*/');
*/
?>