How to replace all XHTML/HTML line breaks (<br>) with new lines?

I would generally say "don't use regex to work with HTML", but, on this one, I would probably go with a regex, considering that <br> tags generally look like either :

  • <br>
  • or <br/>, with any number of spaces before the /


I suppose something like this would do the trick :

$html = 'this <br>is<br/>some<br />text <br    />!';
$nl = preg_replace('#<br\s*/?>#i', "\n", $html);
echo $nl;

Couple of notes :

  • starts with <br
  • followed by any number of white characters : \s*
  • optionnaly, a / : /?
  • and, finally, a >
  • and this using a case-insensitive match (#i), as <BR> would be valid in HTML

If the document is well-formed (or at least well-formed-ish) you can use the DOM extension and xpath to find and replace all br elements by a \n text node.

$in = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html><head><title>...</title></head><body>abc<br />def<p>ghi<br />jkl</p></body></html>';

$doc = new DOMDOcument;
$doc->loadhtml($in);
$xpath = new DOMXPath($doc);

$toBeReplaced = array();
foreach($xpath->query('//br') as $node) {
    $toBeReplaced[] = $node;
}

$linebreak = $doc->createTextNode("\n");
foreach($toBeReplaced as $node) {
    $node->parentNode->replaceChild($linebreak->cloneNode(), $node);
}

echo $doc->savehtml();

prints

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head><title>...</title></head>
<body>abc
def<p>ghi
jkl</p>
</body>
</html>

edit: shorter version with only one iteration

$in = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html><head><title>...</title></head><body>abc<br />def<p>ghi<br />jkl</p></body></html>';

$doc = new DOMDOcument;
$doc->loadhtml($in);
$xpath = new DOMXPath($doc);

$linebreak = $doc->createTextNode("\n");
foreach($xpath->query('//br') as $node) {
  $node->parentNode->removeChild($node);
}

echo $doc->savehtml();

You should be using PHP_EOL constant to have platform independent newlines.

In my opinion, using non-regexp functions whenever possible makes the code more readable.

$newlineTags = array(
  '<br>',
  '<br/>',
  '<br />',
);
$html = str_replace($newlineTags, PHP_EOL, $html);

I am aware this solution has some flaws, but wanted to share my insights still.

Tags:

Php

Regex

Newline

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