whitespace.bom

Code example

A PHP file that starts with a UTF-8 Byte Order Mark (BOM) character (EF BB BF in hex):

<?php declare(strict_types = 1);

echo 'Hello';

The BOM is an invisible character at the very beginning of the file, before the <?php opening tag.

Why is it reported?

The file begins with a UTF-8 BOM (Byte Order Mark) character. While the BOM is valid UTF-8, it causes problems in PHP files:

• When PHP outputs content to the browser, the BOM is sent before any headers, which can cause "headers already sent" errors.
• It can interfere with header(), session_start(), and other functions that must be called before any output.
• It can produce unexpected whitespace in HTML output.

How to fix it

Remove the BOM character from the beginning of the file. Most code editors have an option to save files without BOM:

• In VS Code: Change the encoding in the status bar from "UTF-8 with BOM" to "UTF-8".
• In PhpStorm: Go to File > File Properties > Remove BOM.
• In Sublime Text: Go to File > Save with Encoding > UTF-8.

Alternatively, use a command-line tool to strip the BOM:

sed -i '1s/^\xEF\xBB\xBF//' file.php