Trailing Whitespace

Also Known As

TL;DR

Explanation

Trailing whitespace adds noise to git diffs (lines appear changed when only whitespace changed), can interfere with "headers already sent" errors in PHP if a file ends with whitespace after the closing ?> tag, and makes grep results harder to read. Most editors have a "trim trailing whitespace on save" setting. The PSR-12 standard explicitly prohibits trailing whitespace.

Common Misconception

Why It Matters

Common Mistakes

• Not configuring editors to trim trailing whitespace on save.
• Not adding trailing_whitespace = true to .editorconfig.
• Mixed files where some lines have trailing whitespace and others don't — inconsistent.
• Trailing whitespace in heredoc strings that alters the string content.

Code Examples

function greet(string $name): string {
    return 'Hello ' . $name;   
    //                        ^^^ trailing spaces — invisible but in git diff
}

// .editorconfig fix:
[*]
trim_trailing_whitespace = true

// Trailing whitespace causes noise in diffs and can break heredoc/string comparisons

// .editorconfig
[*.php]
trim_trailing_whitespace = true

// Auto-fix with phpcbf:
$ vendor/bin/phpcbf --standard=PSR12 src/

// Git pre-commit hook to block commits with trailing whitespace:
$ git config core.whitespace trailing-space

// PhpStorm: Settings → Editor → General → Strip trailing spaces on save
// VS Code: "files.trimTrailingWhitespace": true  (in settings.json)

References

• ↗ https://www.php-fig.org/psr/psr-12/

Tags

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