Can I use a hash sign (#) for commenting in PHP?

Question

I have never, ever, seen a PHP file using hashes (#) for commenting. But today I realized that I actually can! I\'m assuming there\'s a reason why everybody uses

Answer 1

One might think that the # form of commenting is primarily intended to make a shell script using the familiar "shebang" (#!) notation. In the following script, PHP should ignore the first line because it is also a comment. Example:

#!/usr/bin/php
<?php

echo "Hello PHP\n";

If you store it in an executable file you can then run it from a terminal like this

./hello

The output is

Hello PHP

However, this reasoning is incorrect, as the following counterexample shows:

#!/usr/bin/php
#A
<?php

#B
echo "Hello PHP\n";

The first line (the shebang line) is specially ignored by the interpreter. The comment line before the PHP tag is echoed to standard output because it is not inside a PHP tag. The comment after the opening PHP tag is interpreted as PHP code but it is ignored because it is a comment.

The output of the revised version is

#A
Hello PHP

Answer 2

From https://php.net/manual/en/migration53.deprecated.php

"Deprecated features in PHP 5.3.x ...Comments starting with '#' are now deprecated in .INI files."

There you have it. Hash '#' appears to remain as a comment option by default by not being deprecated. I plan to use it to distinguish various layers of nested if/else statements and mark their closing brackets, or use to distinguish code comments from commented out code as others have suggested in related posts. (Note: Link was valid/working as of 4/23/19, although who knows if it'll still be working when you're reading this.)

Answer 3

Yes, however there are cross platform differences.

I use # all the time for commenting in PHP, but I have noticed an adoption difference.

On windows keyboard the # key is easy to use. On mac keyboard # key mostly isn't present.

So for mac users, [Alt] + [3] or [⌥] + [3] is more difficult to type than //, so // has become a cross platform way of displaying code with comments.

This is my observation.

Answer 4

Is there any reason, aside from personal preference, to use // rather than # for comments?

I think it is just a personal preference only. There is no difference between // and #. I personally use # for one-line comment, // for commenting out code and /** */ for block comment.

<?php
    # This is a one-line comment
    echo 'This is a test';

    // echo 'This is yet another test'; // commenting code

    /** 
     * This is a block comment
     * with multi-lines 
     */
    echo 'One final test';
?>

Answer 5

PHP's documentation describes the different possibilities of comments. See http://www.php.net/manual/en/language.basic-syntax.comments.php

But it does not say anything about differences between "//" and "#". So there should not be a technical difference. PHP uses C syntax, so I think that is the reason why most of the programmers are using the C-style comments '//'.