Comments

Comments are text placed inside code that is not executed. They are intended as documentation or explanation of the code they are a part of.

Syntax

PHP marks comments in three different ways:

  • // will mark a comment from where it appears until the end of the line (or code block).
  • # will also mark a comment from where it appears until the end of the line (or code block).
  • Multi-line comments are marked by /**/ with everything in between marked as a comment.

Single line comments extend to the end of the line, or the end of the PHP block. ?> will not be commented out, instead, ?> will terminate the comment.

<?php
echo 'Testing 1, 2, 3...' // This is a single line comment
/* This
is
a multi-line comment */
echo 'Hello World!' # This is another single-line comment
// This comment ends with the enclosing block ?>

Note that attempting to nest multi-line comments will result in an error. The first comment ends when the first */ is encountered, leaving the remaining comment(s) to be executed.

<?php
/* This is one multi-line comment
/* But this inner comment will cause problems */
This part of the comment will be executed
since the end of the inner comment ended the outer
comment as well. */
?>
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