How to replace all XHTML/HTML line breaks (<br>) with new lines?
I am looking for the best br2nl function. I would like to replace all instances of <br><br />\n. Much like the nl2br() function but the opposite.
I know there are several solutions in the PHP manual comments but I'm looking for feedback from the SO community on possible solutions.
Solution 1:
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
Solution 2:
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.
Solution 3:
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();