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Комментарии

PHP поддерживает комметарии в стиле 'C', 'C++' и оболочки Unix. Например:

<?php
    
echo "Это тест"// Это однострочный комментарий в стиле c++
    /* Это многострочный комментарий
       еще одна строка комментария */
    
echo "Это еще один тест";
    echo 
"Последний тест"# Это комментарий в стиле оболочки Unix
?>

Однострочные комментарии идут только до конца строки или текущего блока PHP-кода, в зависимости от того, что идет перед ними.

<h1>Это <?php # echo "простой";?> пример.</h1>
<p>Заголовок вверху выведет 'Это пример'.

Будьте внимательны, следите за отсутствием вложенных 'C'-комментариев, они могут появиться во время комментирования больших блоков.

<?php
 
/* 
    echo "Это тест"; /* Этот комментарий вызовет проблему */
 
*/
?>

Однострочные комментарии идут только до конца строки или текущего блока PHP-кода, в зависимости от того, что идет перед ними. Это означает, что HTML-код после // ?> БУДЕТ напечатан: ?> выводит из режима PHP и возвращает в режим HTML, но // не позволяет этого сделать. Если включена конфигурационная директива asp_tags, то же самое происходит и при // %>.


User Contributed Notes
Comments
Wolfsbay at ya dot ru
12-May-2010 09:10
If you are using editor with code highlight, it�_Ts much easier to notice error like /* */ */.
theblazingangel at aol dot com
28-Aug-2007 10:55
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
14-Jul-2006 05:28
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 12:38
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 06:39
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 09:46
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 04:30
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 08:51
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 07:15
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 12:41
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.*/
');

*/

?>
 

 
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