New line to paragraph function - php

Question

I have this interesting function that I'm using to create new lines into paragraphs. I'm using it instead of the nl2br() function, as it outputs better formatted text.
function nl2p($string, $line_breaks = true, $xml = true) {
$string = str_replace(array('<p>', '</p>', '<br>', '<br />'), '', $string);
// It is conceivable that people might still want single line-breaks
// without breaking into a new paragraph.
if ($line_breaks == true)
return '<p>'.preg_replace(array("/([\n]{2,})/i", "/([^>])\n([^<])/i"), array("</p>\n<p>", '<br'.($xml == true ? ' /' : '').'>'), trim($string)).'</p>';
else
return '<p>'.preg_replace(
array("/([\n]{2,})/i", "/([\r\n]{3,})/i","/([^>])\n([^<])/i"),
array("</p>\n<p>", "</p>\n<p>", '<br'.($xml == true ? ' /' : '').'>'),
trim($string)).'</p>';
}
The problem is that whenever I try to create a single line break, it inadvertently removes the first character of the paragraph below it. I'm not familiar enough with regex to understand what is causing the problem.

Answer 1

Here is another approach that doesn't use regular expressions. Note, this function will remove any single line-breaks.
function nl2p($string)
{
$paragraphs = '';
foreach (explode("\n", $string) as $line) {
if (trim($line)) {
$paragraphs .= '<p>' . $line . '</p>';
}
}
return $paragraphs;
}
If you only need to do this once in your app and don't want to create a function, it can easily be done inline:
<?php foreach (explode("\n", $string) as $line): ?>
<?php if (trim($line)): ?>
<p><?=$line?></p>
<?php endif ?>
<?php endforeach ?>

Answer 2

The problem is with your match for single line breaks. It matches the last character before the line break and the first after. Then you replace the match with <br>, so you lose those characters as well. You need to keep them in the replacement.
Try this:
function nl2p($string, $line_breaks = true, $xml = true) {
$string = str_replace(array('<p>', '</p>', '<br>', '<br />'), '', $string);
// It is conceivable that people might still want single line-breaks
// without breaking into a new paragraph.
if ($line_breaks == true)
return '<p>'.preg_replace(array("/([\n]{2,})/i", "/([^>])\n([^<])/i"), array("</p>\n<p>", '$1<br'.($xml == true ? ' /' : '').'>$2'), trim($string)).'</p>';
else
return '<p>'.preg_replace(
array("/([\n]{2,})/i", "/([\r\n]{3,})/i","/([^>])\n([^<])/i"),
array("</p>\n<p>", "</p>\n<p>", '$1<br'.($xml == true ? ' /' : '').'>$2'),
trim($string)).'</p>';
}

Answer 3

I also wrote a very simple version:
function nl2p($text)
{
return '<p>' . str_replace(['\r\n', '\r', '\n'], '</p><p>', $text) . '</p>';
}

Answer 4

#Laurent's answer wasn't working for me - the else statement was doing what the $line_breaks == true statement should have been doing, and it was making multiple line breaks into <br> tags, which PHP's native nl2br() already does.
Here's what I managed to get working with the expected behavior:
function nl2p( $string, $line_breaks = true, $xml = true ) {
// Remove current tags to avoid double-wrapping.
$string = str_replace( array( '<p>', '</p>', '<br>', '<br />' ), '', $string );
// Default: Use <br> for single line breaks, <p> for multiple line breaks.
if ( $line_breaks == true ) {
$string = '<p>' . preg_replace(
array( "/([\n]{2,})/i", "/([\r\n]{3,})/i", "/([^>])\n([^<])/i" ),
array( "</p>\n<p>", "</p>\n<p>", '$1<br' . ( $xml == true ? ' /' : '' ) . '>$2' ),
trim( $string ) ) . '</p>';
// Use <p> for all line breaks if $line_breaks is set to false.
} else {
$string = '<p>' . preg_replace(
array( "/([\n]{1,})/i", "/([\r]{1,})/i" ),
"</p>\n<p>",
trim( $string ) ) . '</p>';
}
// Remove empty paragraph tags.
$string = str_replace( '<p></p>', '', $string );
// Return string.
return $string;
}

Answer 5

Here's an approach that comes with a reverse method to replace paragraphs back to regular line breaks and vice versa.
These are useful to use when building a form input. When saving a users input you may want to convert line breaks to paragraph tags, however when editing the text in a form, you may not want the user to see any html characters. Then we would replace the paragraphs back to line breaks.
// This function will convert newlines to HTML paragraphs
// without paying attention to HTML tags. Feed it a raw string and it will
// simply return that string sectioned into HTML paragraphs
function nl2p($str) {
$arr=explode("\n",$str);
$out='';
for($i=0;$i<count($arr);$i++) {
if(strlen(trim($arr[$i]))>0)
$out.='<p>'.trim($arr[$i]).'</p>';
}
return $out;
}
// Return paragraph tags back to line breaks
function p2nl($str)
{
$str = preg_replace("/<p[^>]*?>/", "", $str);
$str = str_replace("</p>", "\r\n", $str);
return $str;
}

Answer 6

Expanding upon #NaturalBornCamper's solution:
function nl2p( $text, $class = '' ) {
$string = str_replace( array( "\r\n\r\n", "\n\n" ), '</p><p>', $text);
$string = str_replace( array( "\r\n", "\n" ), '<br />', $string);
return '<p' . ( $class ? ' class="' . $class . '"' : '' ) . '>' . $string . '</p>';
}
This takes care of both double line breaks by converting them to paragraphs, and single line breaks by converting them to <br />

Answer 7

Just type this between your lines:
echo '<br>';
This will give you a new line.