PHP Newline: \n, PHP_EOL and nl2br

Write \n inside a double-quoted string to print a new line: echo "Line 1\nLine 2";. The constant PHP_EOL does the same and reads more clearly at the end of a line: echo 'Done' . PHP_EOL;. In a web page, a newline does not show up as a line break; there you need <br> or nl2br().

<?php
echo "Line 1\nLine 2\n";
echo 'Done' . PHP_EOL;

echo "Name:\tAda\n";      // \t is a tab
echo "Language:\tPHP\n";

Single quotes vs double quotes

Escape sequences such as \n and \t only work in double quotes. In single quotes, '\n' is two characters: a backslash and the letter n. This is the usual reason "\n does not work".

<?php
echo 'Single: one\ntwo', "\n";
echo "Double: one\ntwo", "\n";

echo strlen('\n'), "\n";  // 2 characters
echo strlen("\n"), "\n";  // 1 character

// Joining single-quoted text with a newline
echo 'one' . "\n" . 'two' . PHP_EOL;

The strings page lists every escape sequence double quotes understand.

PHP_EOL vs "\n"

PHP_EOL is the line ending of the system PHP is running on: "\n" on Linux and macOS, "\r\n" on Windows. Use it for terminal output and files you will read on the same machine. When a format defines its own line ending, use that instead: HTTP headers and email need "\r\n", and most tools read "\n" fine everywhere.

<?php
var_dump(PHP_EOL);
var_dump(PHP_EOL === "\n");

$lines = ['apples', 'pears', 'plums'];
file_put_contents('list.txt', implode(PHP_EOL, $lines) . PHP_EOL);

echo file_get_contents('list.txt');
echo "Lines in file: ", count(file('list.txt')), "\n";

"\r" is a carriage return, "\n" a line feed. Windows files end lines with both, "\r\n", which is why text from a Windows user or a <textarea> often contains \r characters you did not expect.

New line in HTML: br and nl2br

A browser collapses newlines into a single space, so echo "a\nb" shows a b on a page. Either print <br> yourself, or keep the newlines in your text and convert them with nl2br(), which inserts <br /> before each one. Run this and compare the Output and Page tabs:

<?php
$address = "221B Baker Street\nLondon\nNW1 6XE";

echo "<p><strong>Raw newlines:</strong> ", $address, "</p>\n";
echo "<p><strong>With nl2br:</strong><br>", nl2br($address), "</p>\n";
echo "<p><strong>With pre:</strong></p><pre>", $address, "</pre>\n";

On the Output tab all three look similar. On the Page tab the first one runs together on one line, nl2br() breaks it, and <pre> keeps the newlines as written.

Show textarea input with its line breaks

Text from a <textarea> keeps the lines the user typed, but you must escape it before printing it into HTML. The order matters: htmlspecialchars() first, then nl2br(), otherwise the <br /> tags themselves would be escaped. Run it, type a few lines into the box and press Preview: the same script runs again with $_POST filled in.

<?php
$note = $_POST['note'] ?? '';
?>
<form method="post">
    <textarea name="note" rows="4" cols="30"><?= htmlspecialchars($note) ?></textarea><br>
    <button>Preview</button>
</form>
<?php if ($note !== ''): ?>
    <h3>Preview</h3>
    <p><?= nl2br(htmlspecialchars($note)) ?></p>
    <p><?= substr_count($note, "\n") + 1 ?> lines</p>
<?php endif; ?>

A textarea line break can arrive as "\r\n" or "\n"; both contain "\n", so counting that character works either way. htmlspecialchars() explains why escaping is not optional here.

Split a string by newline

explode("\n", $text) works for text you created yourself. For text from users or files, the line endings may be "\r\n", "\n" or "\r"; preg_split('/\R/', $text) handles all of them, because \R matches any line break.

<?php
$text = "first\r\nsecond\nthird\rfourth";

$lines = preg_split('/\R/', $text);
print_r($lines);

// explode leaves \r at the end of "first"
$naive = explode("\n", $text);
var_dump($naive[0]);

// Skip empty lines too
$text2 = "a\n\nb\n\n\nc\n";
print_r(preg_split('/\R/', $text2, -1, PREG_SPLIT_NO_EMPTY));

Remove line breaks from a string

To turn multi-line text into one line, replace every kind of line ending. Replace "\r\n" before the single characters, or each Windows line break would become two spaces:

<?php
$text = "Hello\r\nworld\nfrom\rPHP\n";

$oneLine = str_replace(["\r\n", "\r", "\n"], ' ', $text);
var_dump($oneLine);

$regex = preg_replace('/\R/', ' ', $text);
var_dump(trim($regex));

// Only the newline at the end
var_dump(rtrim("last line\n", "\r\n"));

trim() and rtrim() remove newlines at the ends of a string but never in the middle, so they are the right tool for a line read from a file and the wrong one for joining lines.