[FIXED] Limited number of break lines in text in PHP

Issue

Assume a string is like

Section 1

Section 2 (after 1 line break)


Section 3 (after 2 line breaks)




Section 4 (after 4 line breaks)

Section 5 (after 1 line break)

My intention is to only allow N number of breaks and replace the other ones with SPACE in PHP. For example, if N=3 then the text above would be outputed like:

Section 1

Section 2 (after 1 line break)

Section 3 (after 2 line breaks) Section 4 (after 4 line breaks) Section 5 (after 1 line break)

My code is below but I am looking for a better way:

function limitedBreaks($str = '', $n = 5)
{
    $str = nl2br($str);
    $chars = str_split($str);
    $counter = 0;
    foreach ($chars as $key => $char) {
        if ($char == "<br/>")
            if ($counter > $n) {
                $chars[$key] = ' ';
            } else {
                $counter += 1;
            }
    }

    return implode($chars, ' ');

}

Solution

This really is a job better suited for regex than exploding and iterating.

$str = preg_replace('~\v+~', "\n\n", $str);

Here \v+ matches any number of vertical spaces, substituted with two \n newlines. You will get a standard one line gap between your content (non-linebreak-only) lines. This results in:

Section 1

Section 2 (after 1 line break)

Section 3 (after 2 line breaks)

Section 4 (after 4 line breaks)

Section 5 (after 1 line break)

If you want to only target more than N breaks, use e.g. \v{4,}, assuming EOL is \n, to normalize all instances of 4 or more newlines. If your file uses Windows EOL (\r\n), be aware that you need to double it up, or use (\r\n|\n){4,}, since \r and \n each are one match of \v.

That's the basic idea. Seeing as you want to replace 4+ newlines with horizontal space, merging the lines instead of normalizing line break quantity, you would simply:

$str = preg_replace('~(\r\n|\n){4,}~', " ", $str);

This would give you:

Section 1

Section 2 (after 1 line break)


Section 3 (after 2 line breaks) Section 4 (after 4 line breaks)

Section 5 (after 1 line break)

Here the gap with 4 or more EOLs was substituted with space and merged with the preceding line. The rest of the "acceptably spaced" lines are still in their places.

---

However it seems that you want to merge all subsequent rows into a single line after any gap of 4+ EOLs. Is that really the requirement? The first example I posted is a fairly standard operation for normalizing content with irregular linebreaks; especially "level items" like section headings!

---

OP: thanks for explaining your use case, makes sense. This can be regex-ed without loops:

$str = preg_replace_callback('~(\r\n|\n){4,}(?<therest>.+)~s', function($match) {
    return ' ' . preg_replace('~\v+~', ' ', $match['therest']);
}, $str);

Here we capture (as named group therest) all the content that follows four or more linebreaks using preg_replace_callback, and inside the callback we preg_replace all vertical spaces in "the rest" with a single horizontal space. This results in:

Section 1

Section 2 (after 1 line break)


Section 3 (after 2 line breaks) Section 4 (after 4 line breaks) Section 5 (after 1 line break) Section 17 after a hundred bundred line breaks"

For convenience, here's the regex above wrapped in a function:

function fuse_breaks(string $str): string {
    $str = preg_replace_callback('~(\r\n|\n){4,}(?<therest>.+)~s', function($match) {
        return ' ' . preg_replace('~\v+~', ' ', $match['therest']);
    }, $str);
    return $str;
}

// Usage:
$fused_text = fuse_breaks($source_text);

Answered By - Markus AO