PHP - Комментарии

Типы

PHP Manual

<?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 // %>.

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PHP Manual

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.*/');

                

                */

                

                ?>