Which Comment Styles Are Not Allowed in PHP? Detailed Explanation of Unsupported Comment Syntax

Which Comment Styles Are Not Allowed in PHP?

In PHP development, using comments helps developers better understand and maintain code. However, PHP enforces certain rules regarding comment styles, and some comment formats are not supported. This article focuses on two comment styles that cannot be used in PHP, helping you avoid incompatible code during development.

Limitations of Single-Line Comments (//) in PHP

In many programming languages, double slashes // are commonly used to indicate single-line comments. While PHP generally supports double-slash comments, some specific environments or interpreter versions may not fully support them, so it is recommended to avoid relying solely on this comment style in certain projects to ensure maximum compatibility.

Why Perl-Style Comments (#!) Are Not Suitable for PHP

In Perl, lines starting with #! usually serve as a shebang to specify the script interpreter rather than a comment itself. PHP does not recognize this syntax as a comment, so using #! may cause code execution errors or parsing issues. Therefore, it should be avoided in PHP code.

Code Examples

// This is a single-line comment (may not be supported in some PHP environments)
#! This is a Perl-style comment (not recognized by PHP)

Summary

Although PHP supports multiple comment styles, developers should avoid using unsupported comment formats, especially Perl-style #! and potentially problematic single-line // comments in some environments. It is recommended to use standard PHP comment styles (such as /* ... */ and # for single-line comments) to ensure code compatibility and maintainability.